Small Data Transmission Assistance Information

ABSTRACT

A second base station sends to a first base station, a request for a context of a wireless device, wherein the request comprises assistance information for a small data transmission (SDT) procedure of the wireless device. The assistance information indicates whether single data associated with the SDT procedure is expected, or more than single data associated with the SDT procedure is expected.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/715,180, filed Apr. 7, 2022, which is a continuation of InternationalPatent Application No. PCT/US2021/017742, filed Feb. 12, 2021, whichclaims the benefit of U.S. Provisional Application No. 62/975,900, filedFeb. 13, 2020, all of which are hereby incorporated by reference intheir entireties.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of several of the various embodiments of the present disclosureare described herein with reference to the drawings.

FIG. 1A and FIG. 1B illustrate example mobile communication networks inwhich embodiments of the present disclosure may be implemented.

FIG. 2A and FIG. 2B respectively illustrate a New Radio (NR) user planeand control plane protocol stack.

FIG. 3 illustrates an example of services provided between protocollayers of the NR user plane protocol stack of FIG. 2A.

FIG. 4A illustrates an example downlink data flow through the NR userplane protocol stack of FIG. 2A.

FIG. 4B illustrates an example format of a MAC subheader in a MAC PDU.

FIG. 5A and FIG. 5B respectively illustrate a mapping between logicalchannels, transport channels, and physical channels for the downlink anduplink.

FIG. 6 is an example diagram showing RRC state transitions of a UE.

FIG. 7 illustrates an example configuration of an NR frame into whichOFDM symbols are grouped.

FIG. 8 illustrates an example configuration of a slot in the time andfrequency domain for an NR carrier.

FIG. 9 illustrates an example of bandwidth adaptation using threeconfigured BWPs for an NR carrier.

FIG. 10A illustrates three carrier aggregation configurations with twocomponent carriers.

FIG. 10B illustrates an example of how aggregated cells may beconfigured into one or more PUCCH groups.

FIG. 11A illustrates an example of an SS/PBCH block structure andlocation.

FIG. 11B illustrates an example of CSI-RSs that are mapped in the timeand frequency domains.

FIG. 12A and FIG. 12B respectively illustrate examples of three downlinkand uplink beam management procedures.

FIG. 13A, FIG. 13B, and FIG. 13C respectively illustrate a four-stepcontention-based random access procedure, a two-step contention-freerandom access procedure, and another two-step random access procedure.

FIG. 14A illustrates an example of CORESET configurations for abandwidth part.

FIG. 14B illustrates an example of a CCE-to-REG mapping for DCItransmission on a CORESET and PDCCH processing.

FIG. 15 illustrates an example of a wireless device in communicationwith a base station.

FIG. 16A, FIG. 16B, FIG. 16C, and FIG. 16D illustrate example structuresfor uplink and downlink transmission.

FIG. 17 illustrates an example of an RRC connection reestablishmentprocedure.

FIG. 18 illustrates an example of an RRC connection resume procedure.

FIG. 19 illustrates an example of an RRC connection resume procedurewith anchor relocation.

FIG. 20 illustrates an example of an RRC connection resume procedurewithout anchor relocation.

FIG. 21 illustrates an example of a control plane early datatransmission procedure.

FIG. 22 illustrates an example of a user plane early data transmissionprocedure with anchor relocation.

FIG. 23 illustrates an example of optimal path for data transmission inmobility of a wireless device.

FIG. 24 illustrates an example of diagram showing an enhanced procedurefor an anchor relocation determination in RRC inactive state.

FIG. 25 illustrates an enhanced procedure for mobile originated datatransmission without anchor relocation in RRC inactive state.

FIG. 26 illustrates an example of an enhanced procedure for mobileterminated data transmission without anchor relocation in RRC inactivestate.

FIG. 27 illustrates an example of diagram showing an enhanced procedurefor an anchor relocation determination in RRC idle state.

FIG. 28 illustrates an example of an enhanced procedure for mobileoriginated data transmission without anchor relocation in RRC idlestate.

FIG. 29 illustrates an example of an enhanced procedure for mobileoriginated data transmission with anchor relocation in RRC idle state.

FIG. 30 illustrates an example of an enhanced procedure with signalingoptimization for mobile originated small data transmission with anchorrelocation in RRC idle state.

DETAILED DESCRIPTION

In the present disclosure, various embodiments are presented as examplesof how the disclosed techniques may be implemented and/or how thedisclosed techniques may be practiced in environments and scenarios. Itwill be apparent to persons skilled in the relevant art that variouschanges in form and detail can be made therein without departing fromthe scope. In fact, after reading the description, it will be apparentto one skilled in the relevant art how to implement alternativeembodiments. The present embodiments should not be limited by any of thedescribed exemplary embodiments. The embodiments of the presentdisclosure will be described with reference to the accompanyingdrawings. Limitations, features, and/or elements from the disclosedexample embodiments may be combined to create further embodiments withinthe scope of the disclosure. Any figures which highlight thefunctionality and advantages, are presented for example purposes only.The disclosed architecture is sufficiently flexible and configurable,such that it may be utilized in ways other than that shown. For example,the actions listed in any flowchart may be re-ordered or only optionallyused in some embodiments.

Embodiments may be configured to operate as needed. The disclosedmechanism may be performed when certain criteria are met, for example,in a wireless device, a base station, a radio environment, a network, acombination of the above, and/or the like. Example criteria may bebased, at least in part, on for example, wireless device or network nodeconfigurations, traffic load, initial system set up, packet sizes,traffic characteristics, a combination of the above, and/or the like.When the one or more criteria are met, various example embodiments maybe applied. Therefore, it may be possible to implement exampleembodiments that selectively implement disclosed protocols.

A base station may communicate with a mix of wireless devices. Wirelessdevices and/or base stations may support multiple technologies, and/ormultiple releases of the same technology. Wireless devices may have somespecific capability(ies) depending on wireless device category and/orcapability(ies). When this disclosure refers to a base stationcommunicating with a plurality of wireless devices, this disclosure mayrefer to a subset of the total wireless devices in a coverage area. Thisdisclosure may refer to, for example, a plurality of wireless devices ofa given LTE or 5G release with a given capability and in a given sectorof the base station. The plurality of wireless devices in thisdisclosure may refer to a selected plurality of wireless devices, and/ora subset of total wireless devices in a coverage area which performaccording to disclosed methods, and/or the like. There may be aplurality of base stations or a plurality of wireless devices in acoverage area that may not comply with the disclosed methods, forexample, those wireless devices or base stations may perform based onolder releases of LTE or 5G technology.

In this disclosure, “a” and “an” and similar phrases are to beinterpreted as “at least one” and “one or more.” Similarly, any termthat ends with the suffix “(s)” is to be interpreted as “at least one”and “one or more.” In this disclosure, the term “may” is to beinterpreted as “may, for example.” In other words, the term “may” isindicative that the phrase following the term “may” is an example of oneof a multitude of suitable possibilities that may, or may not, beemployed by one or more of the various embodiments. The terms“comprises” and “consists of”, as used herein, enumerate one or morecomponents of the element being described. The term “comprises” isinterchangeable with “includes” and does not exclude unenumeratedcomponents from being included in the element being described. Bycontrast, “consists of” provides a complete enumeration of the one ormore components of the element being described. The term “based on”, asused herein, should be interpreted as “based at least in part on” ratherthan, for example, “based solely on”. The term “and/or” as used hereinrepresents any possible combination of enumerated elements. For example,“A, B, and/or C” may represent A; B; C; A and B; A and C; B and C; or A,B, and C.

If A and B are sets and every element of A is an element of B, A iscalled a subset of B. In this specification, only non-empty sets andsubsets are considered. For example, possible subsets of B={cell1,cell2} are: {cell1}, {cell2}, and {cell1, cell2}. The phrase “based on”(or equally “based at least on”) is indicative that the phrase followingthe term “based on” is an example of one of a multitude of suitablepossibilities that may, or may not, be employed to one or more of thevarious embodiments. The phrase “in response to” (or equally “inresponse at least to”) is indicative that the phrase following thephrase “in response to” is an example of one of a multitude of suitablepossibilities that may, or may not, be employed to one or more of thevarious embodiments. The phrase “depending on” (or equally “depending atleast to”) is indicative that the phrase following the phrase “dependingon” is an example of one of a multitude of suitable possibilities thatmay, or may not, be employed to one or more of the various embodiments.The phrase “employing/using” (or equally “employing/using at least”) isindicative that the phrase following the phrase “employing/using” is anexample of one of a multitude of suitable possibilities that may, or maynot, be employed to one or more of the various embodiments.

The term configured may relate to the capacity of a device whether thedevice is in an operational or non-operational state. Configured mayrefer to specific settings in a device that effect the operationalcharacteristics of the device whether the device is in an operational ornon-operational state. In other words, the hardware, software, firmware,registers, memory values, and/or the like may be “configured” within adevice, whether the device is in an operational or nonoperational state,to provide the device with specific characteristics. Terms such as “acontrol message to cause in a device” may mean that a control messagehas parameters that may be used to configure specific characteristics ormay be used to implement certain actions in the device, whether thedevice is in an operational or non-operational state.

In this disclosure, parameters (or equally called, fields, orInformation elements: IEs) may comprise one or more information objects,and an information object may comprise one or more other objects. Forexample, if parameter (IE) N comprises parameter (IE) M, and parameter(IE) M comprises parameter (IE) K, and parameter (IE) K comprisesparameter (information element) J. Then, for example, N comprises K, andN comprises J. In an example embodiment, when one or more messagescomprise a plurality of parameters, it implies that a parameter in theplurality of parameters is in at least one of the one or more messages,but does not have to be in each of the one or more messages.

Many features presented are described as being optional through the useof “may” or the use of parentheses. For the sake of brevity andlegibility, the present disclosure does not explicitly recite each andevery permutation that may be obtained by choosing from the set ofoptional features. The present disclosure is to be interpreted asexplicitly disclosing all such permutations. For example, a systemdescribed as having three optional features may be embodied in sevenways, namely with just one of the three possible features, with any twoof the three possible features or with three of the three possiblefeatures.

Many of the elements described in the disclosed embodiments may beimplemented as modules. A module is defined here as an element thatperforms a defined function and has a defined interface to otherelements. The modules described in this disclosure may be implemented inhardware, software in combination with hardware, firmware, wetware (e.g.hardware with a biological element) or a combination thereof, which maybe behaviorally equivalent. For example, modules may be implemented as asoftware routine written in a computer language configured to beexecuted by a hardware machine (such as C, C++, Fortran, Java, Basic,Matlab or the like) or a modeling/simulation program such as Simulink,Stateflow, GNU Octave, or Lab VIEWMathScript. It may be possible toimplement modules using physical hardware that incorporates discrete orprogrammable analog, digital and/or quantum hardware. Examples ofprogrammable hardware comprise: computers, microcontrollers,microprocessors, application-specific integrated circuits (ASICs); fieldprogrammable gate arrays (FPGAs); and complex programmable logic devices(CPLDs). Computers, microcontrollers and microprocessors are programmedusing languages such as assembly, C, C++ or the like. FPGAs, ASICs andCPLDs are often programmed using hardware description languages (HDL)such as VHSIC hardware description language (VHDL) or Verilog thatconfigure connections between internal hardware modules with lesserfunctionality on a programmable device. The mentioned technologies areoften used in combination to achieve the result of a functional module.

FIG. 1A illustrates an example of a mobile communication network 100 inwhich embodiments of the present disclosure may be implemented. Themobile communication network 100 may be, for example, a public landmobile network (PLMN) run by a network operator. As illustrated in FIG.1A, the mobile communication network 100 includes a core network (CN)102, a radio access network (RAN) 104, and a wireless device 106.

The CN 102 may provide the wireless device 106 with an interface to oneor more data networks (DNs), such as public DNs (e.g., the Internet),private DNs, and/or intra-operator DNs. As part of the interfacefunctionality, the CN 102 may set up end-to-end connections between thewireless device 106 and the one or more DNs, authenticate the wirelessdevice 106, and provide charging functionality.

The RAN 104 may connect the CN 102 to the wireless device 106 throughradio communications over an air interface. As part of the radiocommunications, the RAN 104 may provide scheduling, radio resourcemanagement, and retransmission protocols. The communication directionfrom the RAN 104 to the wireless device 106 over the air interface isknown as the downlink and the communication direction from the wirelessdevice 106 to the RAN 104 over the air interface is known as the uplink.Downlink transmissions may be separated from uplink transmissions usingfrequency division duplexing (FDD), time-division duplexing (TDD),and/or some combination of the two duplexing techniques.

The term wireless device may be used throughout this disclosure to referto and encompass any mobile device or fixed (non-mobile) device forwhich wireless communication is needed or usable. For example, awireless device may be a telephone, smart phone, tablet, computer,laptop, sensor, meter, wearable device, Internet of Things (IoT) device,vehicle road side unit (RSU), relay node, automobile, and/or anycombination thereof. The term wireless device encompasses otherterminology, including user equipment (UE), user terminal (UT), accessterminal (AT), mobile station, handset, wireless transmit and receiveunit (WTRU), and/or wireless communication device.

The RAN 104 may include one or more base stations (not shown). The termbase station may be used throughout this disclosure to refer to andencompass a Node B (associated with UMTS and/or 3G standards), anEvolved Node B (eNB, associated with E-UTRA and/or 4G standards), aremote radio head (RRH), a baseband processing unit coupled to one ormore RRHs, a repeater node or relay node used to extend the coveragearea of a donor node, a Next Generation Evolved Node B (ng-eNB), aGeneration Node B (gNB, associated with NR and/or 5G standards), anaccess point (AP, associated with, for example, WiFi or any othersuitable wireless communication standard), and/or any combinationthereof. A base station may comprise at least one gNB Central Unit(gNB-CU) and at least one a gNB Distributed Unit (gNB-DU).

A base station included in the RAN 104 may include one or more sets ofantennas for communicating with the wireless device 106 over the airinterface. For example, one or more of the base stations may includethree sets of antennas to respectively control three cells (or sectors).The size of a cell may be determined by a range at which a receiver(e.g., a base station receiver) can successfully receive thetransmissions from a transmitter (e.g., a wireless device transmitter)operating in the cell. Together, the cells of the base stations mayprovide radio coverage to the wireless device 106 over a wide geographicarea to support wireless device mobility.

In addition to three-sector sites, other implementations of basestations are possible. For example, one or more of the base stations inthe RAN 104 may be implemented as a sectored site with more or less thanthree sectors. One or more of the base stations in the RAN 104 may beimplemented as an access point, as a baseband processing unit coupled toseveral remote radio heads (RRHs), and/or as a repeater or relay nodeused to extend the coverage area of a donor node. A baseband processingunit coupled to RRHs may be part of a centralized or cloud RANarchitecture, where the baseband processing unit may be eithercentralized in a pool of baseband processing units or virtualized. Arepeater node may amplify and rebroadcast a radio signal received from adonor node. A relay node may perform the same/similar functions as arepeater node but may decode the radio signal received from the donornode to remove noise before amplifying and rebroadcasting the radiosignal.

The RAN 104 may be deployed as a homogenous network of macrocell basestations that have similar antenna patterns and similar high-leveltransmit powers. The RAN 104 may be deployed as a heterogeneous network.In heterogeneous networks, small cell base stations may be used toprovide small coverage areas, for example, coverage areas that overlapwith the comparatively larger coverage areas provided by macrocell basestations. The small coverage areas may be provided in areas with highdata traffic (or so-called “hotspots”) or in areas with weak macrocellcoverage. Examples of small cell base stations include, in order ofdecreasing coverage area, microcell base stations, picocell basestations, and femtocell base stations or home base stations.

The Third-Generation Partnership Project (3GPP) was formed in 1998 toprovide global standardization of specifications for mobilecommunication networks similar to the mobile communication network 100in FIG. 1A. To date, 3GPP has produced specifications for threegenerations of mobile networks: a third generation (3G) network known asUniversal Mobile Telecommunications System (UMTS), a fourth generation(4G) network known as Long-Term Evolution (LTE), and a fifth generation(5G) network known as 5G System (5GS). Embodiments of the presentdisclosure are described with reference to the RAN of a 3GPP 5G network,referred to as next-generation RAN (NG-RAN). Embodiments may beapplicable to RANs of other mobile communication networks, such as theRAN 104 in FIG. 1A, the RANs of earlier 3G and 4G networks, and those offuture networks yet to be specified (e.g., a 3GPP 6G network). NG-RANimplements 5G radio access technology known as New Radio (NR) and may beprovisioned to implement 4G radio access technology or other radioaccess technologies, including non-3GPP radio access technologies.

FIG. 1B illustrates another example mobile communication network 150 inwhich embodiments of the present disclosure may be implemented. Mobilecommunication network 150 may be, for example, a PLMN run by a networkoperator. As illustrated in FIG. 1B, mobile communication network 150includes a 5G core network (5G-CN) 152, an NG-RAN 154, and UEs 156A and156B (collectively UEs 156). These components may be implemented andoperate in the same or similar manner as corresponding componentsdescribed with respect to FIG. 1A.

The 5G-CN 152 provides the UEs 156 with an interface to one or more DNs,such as public DNs (e.g., the Internet), private DNs, and/orintra-operator DNs. As part of the interface functionality, the 5G-CN152 may set up end-to-end connections between the UEs 156 and the one ormore DNs, authenticate the UEs 156, and provide charging functionality.Compared to the CN of a 3GPP 4G network, the basis of the 5G-CN 152 maybe a service-based architecture. This means that the architecture of thenodes making up the 5G-CN 152 may be defined as network functions thatoffer services via interfaces to other network functions. The networkfunctions of the 5G-CN 152 may be implemented in several ways, includingas network elements on dedicated or shared hardware, as softwareinstances running on dedicated or shared hardware, or as virtualizedfunctions instantiated on a platform (e.g., a cloud-based platform).

As illustrated in FIG. 1B, the 5G-CN 152 includes an Access and MobilityManagement Function (AMF) 158A and a User Plane Function (UPF) 158B,which are shown as one component AMF/UPF 158 in FIG. 1B for ease ofillustration. The UPF 158B may serve as a gateway between the NG-RAN 154and the one or more DNs. The UPF 158B may perform functions such aspacket routing and forwarding, packet inspection and user plane policyrule enforcement, traffic usage reporting, uplink classification tosupport routing of traffic flows to the one or more DNs, quality ofservice (QoS) handling for the user plane (e.g., packet filtering,gating, uplink/downlink rate enforcement, and uplink trafficverification), downlink packet buffering, and downlink data notificationtriggering. The UPF 158B may serve as an anchor point forintra-/inter-Radio Access Technology (RAT) mobility, an externalprotocol (or packet) data unit (PDU) session point of interconnect tothe one or more DNs, and/or a branching point to support a multi-homedPDU session. The UEs 156 may be configured to receive services through aPDU session, which is a logical connection between a UE and a DN.

The AMF 158A may perform functions such as Non-Access Stratum (NAS)signaling termination, NAS signaling security, Access Stratum (AS)security control, inter-CN node signaling for mobility between 3GPPaccess networks, idle mode UE reachability (e.g., control and executionof paging retransmission), registration area management, intra-systemand inter-system mobility support, access authentication, accessauthorization including checking of roaming rights, mobility managementcontrol (subscription and policies), network slicing support, and/orsession management function (SMF) selection. NAS may refer to thefunctionality operating between a CN and a UE, and AS may refer to thefunctionality operating between the UE and a RAN.

The 5G-CN 152 may include one or more additional network functions thatare not shown in FIG. 1B for the sake of clarity. For example, the 5G-CN152 may include one or more of a Session Management Function (SMF), anNR Repository Function (NRF), a Policy Control Function (PCF), a NetworkExposure Function (NEF), a Unified Data Management (UDM), an ApplicationFunction (AF), and/or an Authentication Server Function (AUSF).

The NG-RAN 154 may connect the 5G-CN 152 to the UEs 156 through radiocommunications over the air interface. The NG-RAN 154 may include one ormore gNBs, illustrated as gNB 160A and gNB 160B (collectively gNBs 160)and/or one or more ng-eNBs, illustrated as ng-eNB 162A and ng-eNB 162B(collectively ng-eNBs 162). The gNBs 160 and ng-eNBs 162 may be moregenerically referred to as base stations. The gNBs 160 and ng-eNBs 162may include one or more sets of antennas for communicating with the UEs156 over an air interface. For example, one or more of the gNBs 160and/or one or more of the ng-eNBs 162 may include three sets of antennasto respectively control three cells (or sectors). Together, the cells ofthe gNBs 160 and the ng-eNBs 162 may provide radio coverage to the UEs156 over a wide geographic area to support UE mobility.

As shown in FIG. 1B, the gNBs 160 and/or the ng-eNBs 162 may beconnected to the 5G-CN 152 by means of an NG interface and to other basestations by an Xn interface. The NG and Xn interfaces may be establishedusing direct physical connections and/or indirect connections over anunderlying transport network, such as an internet protocol (IP)transport network. The gNBs 160 and/or the ng-eNBs 162 may be connectedto the UEs 156 by means of a Uu interface. For example, as illustratedin FIG. 1B, gNB 160A may be connected to the UE 156A by means of a Uuinterface. The NG, Xn, and Uu interfaces are associated with a protocolstack. The protocol stacks associated with the interfaces may be used bythe network elements in FIG. 1B to exchange data and signaling messagesand may include two planes: a user plane and a control plane. The userplane may handle data of interest to a user. The control plane mayhandle signaling messages of interest to the network elements.

The gNBs 160 and/or the ng-eNBs 162 may be connected to one or moreAMF/UPF functions of the 5G-CN 152, such as the AMF/UPF 158, by means ofone or more NG interfaces. For example, the gNB 160A may be connected tothe UPF 158B of the AMF/UPF 158 by means of an NG-User plane (NG-U)interface. The NG-U interface may provide delivery (e.g., non-guaranteeddelivery) of user plane PDUs between the gNB 160A and the UPF 158B. ThegNB 160A may be connected to the AMF 158A by means of an NG-Controlplane (NG-C) interface. The NG-C interface may provide, for example, NGinterface management, UE context management, UE mobility management,transport of NAS messages, paging, PDU session management, andconfiguration transfer and/or warning message transmission.

The gNBs 160 may provide NR user plane and control plane protocolterminations towards the UEs 156 over the Uu interface. For example, thegNB 160A may provide NR user plane and control plane protocolterminations toward the UE 156A over a Uu interface associated with afirst protocol stack. The ng-eNBs 162 may provide Evolved UMTSTerrestrial Radio Access (E-UTRA) user plane and control plane protocolterminations towards the UEs 156 over a Uu interface, where E-UTRArefers to the 3GPP 4G radio-access technology. For example, the ng-eNB162B may provide E-UTRA user plane and control plane protocolterminations towards the UE 156B over a Uu interface associated with asecond protocol stack.

The 5G-CN 152 was described as being configured to handle NR and 4Gradio accesses. It will be appreciated by one of ordinary skill in theart that it may be possible for NR to connect to a 4G core network in amode known as “non-standalone operation.” In non-standalone operation, a4G core network is used to provide (or at least support) control-planefunctionality (e.g., initial access, mobility, and paging). Althoughonly one AMF/UPF 158 is shown in FIG. 1B, one gNB or ng-eNB may beconnected to multiple AMF/UPF nodes to provide redundancy and/or to loadshare across the multiple AMF/UPF nodes.

As discussed, an interface (e.g., Uu, Xn, and NG interfaces) between thenetwork elements in FIG. 1B may be associated with a protocol stack thatthe network elements use to exchange data and signaling messages. Aprotocol stack may include two planes: a user plane and a control plane.The user plane may handle data of interest to a user, and the controlplane may handle signaling messages of interest to the network elements.

FIG. 2A and FIG. 2B respectively illustrate examples of NR user planeand NR control plane protocol stacks for the Uu interface that liesbetween a UE 210 and a gNB 220. The protocol stacks illustrated in FIG.2A and FIG. 2B may be the same or similar to those used for the Uuinterface between, for example, the UE 156A and the gNB 160A shown inFIG. 1B.

FIG. 2A illustrates a NR user plane protocol stack comprising fivelayers implemented in the UE 210 and the gNB 220. At the bottom of theprotocol stack, physical layers (PHYs) 211 and 221 may provide transportservices to the higher layers of the protocol stack and may correspondto layer 1 of the Open Systems Interconnection (OSI) model. The nextfour protocols above PHYs 211 and 221 comprise media access controllayers (MACs) 212 and 222, radio link control layers (RLCs) 213 and 223,packet data convergence protocol layers (PDCPs) 214 and 224, and servicedata application protocol layers (SDAPs) 215 and 225. Together, thesefour protocols may make up layer 2, or the data link layer, of the OSImodel.

FIG. 3 illustrates an example of services provided between protocollayers of the NR user plane protocol stack. Starting from the top ofFIG. 2A and FIG. 3 , the SDAPs 215 and 225 may perform QoS flowhandling. The UE 210 may receive services through a PDU session, whichmay be a logical connection between the UE 210 and a DN. The PDU sessionmay have one or more QoS flows. A UPF of a CN (e.g., the UPF 158B) maymap IP packets to the one or more QoS flows of the PDU session based onQoS requirements (e.g., in terms of delay, data rate, and/or errorrate). The SDAPs 215 and 225 may perform mapping/de-mapping between theone or more QoS flows and one or more data radio bearers. Themapping/de-mapping between the QoS flows and the data radio bearers maybe determined by the SDAP 225 at the gNB 220. The SDAP 215 at the UE 210may be informed of the mapping between the QoS flows and the data radiobearers through reflective mapping or control signaling received fromthe gNB 220. For reflective mapping, the SDAP 225 at the gNB 220 maymark the downlink packets with a QoS flow indicator (QFI), which may beobserved by the SDAP 215 at the UE 210 to determine themapping/de-mapping between the QoS flows and the data radio bearers.

The PDCPs 214 and 224 may perform header compression/decompression toreduce the amount of data that needs to be transmitted over the airinterface, ciphering/deciphering to prevent unauthorized decoding ofdata transmitted over the air interface, and integrity protection (toensure control messages originate from intended sources. The PDCPs 214and 224 may perform retransmissions of undelivered packets, in-sequencedelivery and reordering of packets, and removal of packets received induplicate due to, for example, an intra-gNB handover. The PDCPs 214 and224 may perform packet duplication to improve the likelihood of thepacket being received and, at the receiver, remove any duplicatepackets. Packet duplication may be useful for services that require highreliability.

Although not shown in FIG. 3 , PDCPs 214 and 224 may performmapping/de-mapping between a split radio bearer and RLC channels in adual connectivity scenario. Dual connectivity is a technique that allowsa UE to connect to two cells or, more generally, two cell groups: amaster cell group (MCG) and a secondary cell group (SCG). A split beareris when a single radio bearer, such as one of the radio bearers providedby the PDCPs 214 and 224 as a service to the SDAPs 215 and 225, ishandled by cell groups in dual connectivity. The PDCPs 214 and 224 maymap/de-map the split radio bearer between RLC channels belonging to cellgroups.

The RLCs 213 and 223 may perform segmentation, retransmission throughAutomatic Repeat Request (ARQ), and removal of duplicate data unitsreceived from MACs 212 and 222, respectively. The RLCs 213 and 223 maysupport three transmission modes: transparent mode (TM); unacknowledgedmode (UM); and acknowledged mode (AM). Based on the transmission mode anRLC is operating, the RLC may perform one or more of the notedfunctions. The RLC configuration may be per logical channel with nodependency on numerologies and/or Transmission Time Interval (TTI)durations. As shown in FIG. 3 , the RLCs 213 and 223 may provide RLCchannels as a service to PDCPs 214 and 224, respectively.

The MACs 212 and 222 may perform multiplexing/demultiplexing of logicalchannels and/or mapping between logical channels and transport channels.The multiplexing/demultiplexing may include multiplexing/demultiplexingof data units, belonging to the one or more logical channels, into/fromTransport Blocks (TBs) delivered to/from the PHYs 211 and 221. The MAC222 may be configured to perform scheduling, scheduling informationreporting, and priority handling between UEs by means of dynamicscheduling. Scheduling may be performed in the gNB 220 (at the MAC 222)for downlink and uplink. The MACs 212 and 222 may be configured toperform error correction through Hybrid Automatic Repeat Request (HARQ)(e.g., one HARQ entity per carrier in case of Carrier Aggregation (CA)),priority handling between logical channels of the UE 210 by means oflogical channel prioritization, and/or padding. The MACs 212 and 222 maysupport one or more numerologies and/or transmission timings. In anexample, mapping restrictions in a logical channel prioritization maycontrol which numerology and/or transmission timing a logical channelmay use. As shown in FIG. 3 , the MACs 212 and 222 may provide logicalchannels as a service to the RLCs 213 and 223.

The PHYs 211 and 221 may perform mapping of transport channels tophysical channels and digital and analog signal processing functions forsending and receiving information over the air interface. These digitaland analog signal processing functions may include, for example,coding/decoding and modulation/demodulation. The PHYs 211 and 221 mayperform multi-antenna mapping. As shown in FIG. 3 , the PHYs 211 and 221may provide one or more transport channels as a service to the MACs 212and 222.

FIG. 4A illustrates an example downlink data flow through the NR userplane protocol stack. FIG. 4A illustrates a downlink data flow of threeIP packets (n, n+1, and m) through the NR user plane protocol stack togenerate two TBs at the gNB 220. An uplink data flow through the NR userplane protocol stack may be similar to the downlink data flow depictedin FIG. 4A.

The downlink data flow of FIG. 4A begins when SDAP 225 receives thethree IP packets from one or more QoS flows and maps the three packetsto radio bearers. In FIG. 4A, the SDAP 225 maps IP packets n and n+1 toa first radio bearer 402 and maps IP packet m to a second radio bearer404. An SDAP header (labeled with an “H” in FIG. 4A) is added to an IPpacket. The data unit from/to a higher protocol layer is referred to asa service data unit (SDU) of the lower protocol layer and the data unitto/from a lower protocol layer is referred to as a protocol data unit(PDU) of the higher protocol layer. As shown in FIG. 4A, the data unitfrom the SDAP 225 is an SDU of lower protocol layer PDCP 224 and is aPDU of the SDAP 225.

The remaining protocol layers in FIG. 4A may perform their associatedfunctionality (e.g., with respect to FIG. 3 ), add correspondingheaders, and forward their respective outputs to the next lower layer.For example, the PDCP 224 may perform IP-header compression andciphering and forward its output to the RLC 223. The RLC 223 mayoptionally perform segmentation (e.g., as shown for IP packet m in FIG.4A) and forward its output to the MAC 222. The MAC 222 may multiplex anumber of RLC PDUs and may attach a MAC subheader to an RLC PDU to forma transport block. In NR, the MAC subheaders may be distributed acrossthe MAC PDU, as illustrated in FIG. 4A. In LTE, the MAC subheaders maybe entirely located at the beginning of the MAC PDU. The NR MAC PDUstructure may reduce processing time and associated latency because theMAC PDU subheaders may be computed before the full MAC PDU is assembled.

FIG. 4B illustrates an example format of a MAC subheader in a MAC PDU.The MAC subheader includes: an SDU length field for indicating thelength (e.g., in bytes) of the MAC SDU to which the MAC subheadercorresponds; a logical channel identifier (LCID) field for identifyingthe logical channel from which the MAC SDU originated to aid in thedemultiplexing process; a flag (F) for indicating the size of the SDUlength field; and a reserved bit (R) field for future use.

FIG. 4B further illustrates MAC control elements (CEs) inserted into theMAC PDU by a MAC, such as MAC 223 or MAC 222. For example, FIG. 4Billustrates two MAC CEs inserted into the MAC PDU. MAC CEs may beinserted at the beginning of a MAC PDU for downlink transmissions (asshown in FIG. 4B) and at the end of a MAC PDU for uplink transmissions.MAC CEs may be used for in-band control signaling. Example MAC CEsinclude: scheduling-related MAC CEs, such as buffer status reports andpower headroom reports; activation/deactivation MAC CEs, such as thosefor activation/deactivation of PDCP duplication detection, channel stateinformation (CSI) reporting, sounding reference signal (SRS)transmission, and prior configured components; discontinuous reception(DRX) related MAC CEs; timing advance MAC CEs; and random access relatedMAC CEs. A MAC CE may be preceded by a MAC subheader with a similarformat as described for MAC SDUs and may be identified with a reservedvalue in the LCID field that indicates the type of control informationincluded in the MAC CE.

Before describing the NR control plane protocol stack, logical channels,transport channels, and physical channels are first described as well asa mapping between the channel types. One or more of the channels may beused to carry out functions associated with the NR control planeprotocol stack described later below.

FIG. 5A and FIG. 5B illustrate, for downlink and uplink respectively, amapping between logical channels, transport channels, and physicalchannels. Information is passed through channels between the RLC, theMAC, and the PHY of the NR protocol stack. A logical channel may be usedbetween the RLC and the MAC and may be classified as a control channelthat carries control and configuration information in the NR controlplane or as a traffic channel that carries data in the NR user plane. Alogical channel may be classified as a dedicated logical channel that isdedicated to a specific UE or as a common logical channel that may beused by more than one UE. A logical channel may also be defined by thetype of information it carries. The set of logical channels defined byNR include, for example:

-   -   a paging control channel (PCCH) for carrying paging messages        used to page a UE whose location is not known to the network on        a cell level;    -   a broadcast control channel (BCCH) for carrying system        information messages in the form of a master information block        (MIB) and several system information blocks (SIB s), wherein the        system information messages may be used by the UEs to obtain        information about how a cell is configured and how to operate        within the cell;    -   a common control channel (CCCH) for carrying control messages        together with random access;    -   a dedicated control channel (DCCH) for carrying control messages        to/from a specific the UE to configure the UE; and    -   a dedicated traffic channel (DTCH) for carrying user data        to/from a specific the UE.

Transport channels are used between the MAC and PHY layers and may bedefined by how the information they carry is transmitted over the airinterface. The set of transport channels defined by NR include, forexample:

-   -   a paging channel (PCH) for carrying paging messages that        originated from the PCCH;    -   a broadcast channel (BCH) for carrying the MIB from the BCCH;    -   a downlink shared channel (DL-SCH) for carrying downlink data        and signaling messages, including the SIB s from the BCCH;    -   an uplink shared channel (UL-SCH) for carrying uplink data and        signaling messages; and    -   a random access channel (RACH) for allowing a UE to contact the        network without any prior scheduling.

The PHY may use physical channels to pass information between processinglevels of the PHY. A physical channel may have an associated set oftime-frequency resources for carrying the information of one or moretransport channels. The PHY may generate control information to supportthe low-level operation of the PHY and provide the control informationto the lower levels of the PHY via physical control channels, known asL1/L2 control channels. The set of physical channels and physicalcontrol channels defined by NR include, for example:

-   -   a physical broadcast channel (PBCH) for carrying the MIB from        the BCH;    -   a physical downlink shared channel (PDSCH) for carrying downlink        data and signaling messages from the DL-SCH, as well as paging        messages from the PCH;    -   a physical downlink control channel (PDCCH) for carrying        downlink control information (DCI), which may include downlink        scheduling commands, uplink scheduling grants, and uplink power        control commands;    -   a physical uplink shared channel (PUSCH) for carrying uplink        data and signaling messages from the UL-SCH and in some        instances uplink control information (UCI) as described below;    -   a physical uplink control channel (PUCCH) for carrying UCI,        which may include HARQ acknowledgments, channel quality        indicators (CQI), pre-coding matrix indicators (PMI), rank        indicators (RI), and scheduling requests (SR); and    -   a physical random access channel (PRACH) for random access.

Similar to the physical control channels, the physical layer generatesphysical signals to support the low-level operation of the physicallayer. As shown in FIG. 5A and FIG. 5B, the physical layer signalsdefined by NR include: primary synchronization signals (PSS), secondarysynchronization signals (SSS), channel state information referencesignals (CSI-RS), demodulation reference signals (DMRS), soundingreference signals (SRS), and phase-tracking reference signals (PT-RS).These physical layer signals will be described in greater detail below.

FIG. 2B illustrates an example NR control plane protocol stack. As shownin FIG. 2B, the NR control plane protocol stack may use the same/similarfirst four protocol layers as the example NR user plane protocol stack.These four protocol layers include the PHYs 211 and 221, the MACs 212and 222, the RLCs 213 and 223, and the PDCPs 214 and 224. Instead ofhaving the SDAPs 215 and 225 at the top of the stack as in the NR userplane protocol stack, the NR control plane stack has radio resourcecontrols (RRCs) 216 and 226 and NAS protocols 217 and 237 at the top ofthe NR control plane protocol stack.

The NAS protocols 217 and 237 may provide control plane functionalitybetween the UE 210 and the AMF 230 (e.g., the AMF 158A) or, moregenerally, between the UE 210 and the CN. The NAS protocols 217 and 237may provide control plane functionality between the UE 210 and the AMF230 via signaling messages, referred to as NAS messages. There is nodirect path between the UE 210 and the AMF 230 through which the NASmessages can be transported. The NAS messages may be transported usingthe AS of the Uu and NG interfaces. NAS protocols 217 and 237 mayprovide control plane functionality such as authentication, security,connection setup, mobility management, and session management.

The RRCs 216 and 226 may provide control plane functionality between theUE 210 and the gNB 220 or, more generally, between the UE 210 and theRAN. The RRCs 216 and 226 may provide control plane functionalitybetween the UE 210 and the gNB 220 via signaling messages, referred toas RRC messages. RRC messages may be transmitted between the UE 210 andthe RAN using signaling radio bearers and the same/similar PDCP, RLC,MAC, and PHY protocol layers. The MAC may multiplex control-plane anduser-plane data into the same transport block (TB). The RRCs 216 and 226may provide control plane functionality such as: broadcast of systeminformation related to AS and NAS; paging initiated by the CN or theRAN; establishment, maintenance and release of an RRC connection betweenthe UE 210 and the RAN; security functions including key management;establishment, configuration, maintenance and release of signaling radiobearers and data radio bearers; mobility functions; QoS managementfunctions; the UE measurement reporting and control of the reporting;detection of and recovery from radio link failure (RLF); and/or NASmessage transfer. As part of establishing an RRC connection, RRCs 216and 226 may establish an RRC context, which may involve configuringparameters for communication between the UE 210 and the RAN.

FIG. 6 is an example diagram showing RRC state transitions of a UE. TheUE may be the same or similar to the wireless device 106 depicted inFIG. 1A, the UE 210 depicted in FIG. 2A and FIG. 2B, or any otherwireless device described in the present disclosure. As illustrated inFIG. 6 , a UE may be in at least one of three RRC states: RRC connected602 (e.g., RRC_CONNECTED), RRC idle 604 (e.g., RRC_IDLE), and RRCinactive 606 (e.g., RRC_INACTIVE).

In RRC connected 602, the UE has an established RRC context and may haveat least one RRC connection with a base station. The base station may besimilar to one of the one or more base stations included in the RAN 104depicted in FIG. 1A, one of the gNBs 160 or ng-eNBs 162 depicted in FIG.1B, the gNB 220 depicted in FIG. 2A and FIG. 2B, or any other basestation described in the present disclosure. The base station with whichthe UE is connected may have the RRC context for the UE. The RRCcontext, referred to as the UE context, may comprise parameters forcommunication between the UE and the base station. These parameters mayinclude, for example: one or more AS contexts; one or more radio linkconfiguration parameters; bearer configuration information (e.g.,relating to a data radio bearer, signaling radio bearer, logicalchannel, QoS flow, and/or PDU session); security information; and/orPHY, MAC, RLC, PDCP, and/or SDAP layer configuration information. Whilein RRC connected 602, mobility of the UE may be managed by the RAN(e.g., the RAN 104 or the NG-RAN 154). The UE may measure the signallevels (e.g., reference signal levels) from a serving cell andneighboring cells and report these measurements to the base stationcurrently serving the UE. The UE's serving base station may request ahandover to a cell of one of the neighboring base stations based on thereported measurements. The RRC state may transition from RRC connected602 to RRC idle 604 through a connection release procedure 608 or to RRCinactive 606 through a connection inactivation procedure 610.

In RRC idle 604, an RRC context may not be established for the UE. InRRC idle 604, the UE may not have an RRC connection with the basestation. While in RRC idle 604, the UE may be in a sleep state for themajority of the time (e.g., to conserve battery power). The UE may wakeup periodically (e.g., once in every discontinuous reception cycle) tomonitor for paging messages from the RAN. Mobility of the UE may bemanaged by the UE through a procedure known as cell reselection. The RRCstate may transition from RRC idle 604 to RRC connected 602 through aconnection establishment procedure 612, which may involve a randomaccess procedure as discussed in greater detail below.

In RRC inactive 606, the RRC context previously established ismaintained in the UE and the base station. This allows for a fasttransition to RRC connected 602 with reduced signaling overhead ascompared to the transition from RRC idle 604 to RRC connected 602. Whilein RRC inactive 606, the UE may be in a sleep state and mobility of theUE may be managed by the UE through cell reselection. The RRC state maytransition from RRC inactive 606 to RRC connected 602 through aconnection resume procedure 614 or to RRC idle 604 though a connectionrelease procedure 616 that may be the same as or similar to connectionrelease procedure 608.

An RRC state may be associated with a mobility management mechanism. InRRC idle 604 and RRC inactive 606, mobility is managed by the UE throughcell reselection. The purpose of mobility management in RRC idle 604 andRRC inactive 606 is to allow the network to be able to notify the UE ofan event via a paging message without having to broadcast the pagingmessage over the entire mobile communications network. The mobilitymanagement mechanism used in RRC idle 604 and RRC inactive 606 may allowthe network to track the UE on a cell-group level so that the pagingmessage may be broadcast over the cells of the cell group that the UEcurrently resides within instead of the entire mobile communicationnetwork. The mobility management mechanisms for RRC idle 604 and RRCinactive 606 track the UE on a cell-group level. They may do so usingdifferent granularities of grouping. For example, there may be threelevels of cell-grouping granularity: individual cells; cells within aRAN area identified by a RAN area identifier (RAI); and cells within agroup of RAN areas, referred to as a tracking area and identified by atracking area identifier (TAI).

Tracking areas may be used to track the UE at the CN level. The CN(e.g., the CN 102 or the 5G-CN 152) may provide the UE with a list ofTAIs associated with a UE registration area. If the UE moves, throughcell reselection, to a cell associated with a TAI not included in thelist of TAIs associated with the UE registration area, the UE mayperform a registration update with the CN to allow the CN to update theUE's location and provide the UE with a new the UE registration area.

RAN areas may be used to track the UE at the RAN level. For a UE in RRCinactive 606 state, the UE may be assigned a RAN notification area. ARAN notification area may comprise one or more cell identities, a listof RAIs, or a list of TAIs. In an example, a base station may belong toone or more RAN notification areas. In an example, a cell may belong toone or more RAN notification areas. If the UE moves, through cellreselection, to a cell not included in the RAN notification areaassigned to the UE, the UE may perform a notification area update withthe RAN to update the UE's RAN notification area.

A base station storing an RRC context for a UE or a last serving basestation of the UE may be referred to as an anchor base station. Ananchor base station may maintain an RRC context for the UE at leastduring a period of time that the UE stays in a RAN notification area ofthe anchor base station and/or during a period of time that the UE staysin RRC inactive 606.

A gNB, such as gNBs 160 in FIG. 1B, may be split in two parts: a centralunit (gNB-CU), and one or more distributed units (gNB-DU). A gNB-CU maybe coupled to one or more gNB-DUs using an F1 interface. The gNB-CU maycomprise the RRC, the PDCP, and the SDAP. A gNB-DU may comprise the RLC,the MAC, and the PHY.

In NR, the physical signals and physical channels (discussed withrespect to FIG. 5A and FIG. 5B) may be mapped onto orthogonal frequencydivisional multiplexing (OFDM) symbols. OFDM is a multicarriercommunication scheme that transmits data over F orthogonal subcarriers(or tones). Before transmission, the data may be mapped to a series ofcomplex symbols (e.g., M-quadrature amplitude modulation (M-QAM) orM-phase shift keying (M-PSK) symbols), referred to as source symbols,and divided into F parallel symbol streams. The F parallel symbolstreams may be treated as though they are in the frequency domain andused as inputs to an Inverse Fast Fourier Transform (IFFT) block thattransforms them into the time domain. The IFFT block may take in Fsource symbols at a time, one from each of the F parallel symbolstreams, and use each source symbol to modulate the amplitude and phaseof one of F sinusoidal basis functions that correspond to the Forthogonal subcarriers. The output of the IFFT block may be Ftime-domain samples that represent the summation of the F orthogonalsubcarriers. The F time-domain samples may form a single OFDM symbol.After some processing (e.g., addition of a cyclic prefix) andup-conversion, an OFDM symbol provided by the IFFT block may betransmitted over the air interface on a carrier frequency. The Fparallel symbol streams may be mixed using an FFT block before beingprocessed by the IFFT block. This operation produces Discrete FourierTransform (DFT)-precoded OFDM symbols and may be used by UEs in theuplink to reduce the peak to average power ratio (PAPR). Inverseprocessing may be performed on the OFDM symbol at a receiver using anFFT block to recover the data mapped to the source symbols.

FIG. 7 illustrates an example configuration of an NR frame into whichOFDM symbols are grouped. An NR frame may be identified by a systemframe number (SFN). The SFN may repeat with a period of 1024 frames. Asillustrated, one NR frame may be 10 milliseconds (ms) in duration andmay include 10 subframes that are 1 ms in duration. A subframe may bedivided into slots that include, for example, 14 OFDM symbols per slot.

The duration of a slot may depend on the numerology used for the OFDMsymbols of the slot. In NR, a flexible numerology is supported toaccommodate different cell deployments (e.g., cells with carrierfrequencies below 1 GHz up to cells with carrier frequencies in themm-wave range). A numerology may be defined in terms of subcarrierspacing and cyclic prefix duration. For a numerology in NR, subcarrierspacings may be scaled up by powers of two from a baseline subcarrierspacing of 15 kHz, and cyclic prefix durations may be scaled down bypowers of two from a baseline cyclic prefix duration of 4.7 μs. Forexample, NR defines numerologies with the following subcarrierspacing/cyclic prefix duration combinations: 15 kHz/4.7 μs; 30 kHz/2.3μs; 60 kHz/1.2 μs; 120 kHz/0.59 μs; and 240 kHz/0.29 μs.

A slot may have a fixed number of OFDM symbols (e.g., 14 OFDM symbols).A numerology with a higher subcarrier spacing has a shorter slotduration and, correspondingly, more slots per subframe. FIG. 7illustrates this numerology-dependent slot duration andslots-per-subframe transmission structure (the numerology with asubcarrier spacing of 240 kHz is not shown in FIG. 7 for ease ofillustration). A subframe in NR may be used as a numerology-independenttime reference, while a slot may be used as the unit upon which uplinkand downlink transmissions are scheduled. To support low latency,scheduling in NR may be decoupled from the slot duration and start atany OFDM symbol and last for as many symbols as needed for atransmission. These partial slot transmissions may be referred to asmini-slot or subslot transmissions.

FIG. 8 illustrates an example configuration of a slot in the time andfrequency domain for an NR carrier. The slot includes resource elements(REs) and resource blocks (RBs). An RE is the smallest physical resourcein NR. An RE spans one OFDM symbol in the time domain by one subcarrierin the frequency domain as shown in FIG. 8 . An RB spans twelveconsecutive REs in the frequency domain as shown in FIG. 8 . An NRcarrier may be limited to a width of 275 RBs or 275×12=3300 subcarriers.Such a limitation, if used, may limit the NR carrier to 50, 100, 200,and 400 MHz for subcarrier spacings of 15, 30, 60, and 120 kHz,respectively, where the 400 MHz bandwidth may be set based on a 400 MHzper carrier bandwidth limit.

FIG. 8 illustrates a single numerology being used across the entirebandwidth of the NR carrier. In other example configurations, multiplenumerologies may be supported on the same carrier.

NR may support wide carrier bandwidths (e.g., up to 400 MHz for asubcarrier spacing of 120 kHz). Not all UEs may be able to receive thefull carrier bandwidth (e.g., due to hardware limitations). Also,receiving the full carrier bandwidth may be prohibitive in terms of UEpower consumption. In an example, to reduce power consumption and/or forother purposes, a UE may adapt the size of the UE's receive bandwidthbased on the amount of traffic the UE is scheduled to receive. This isreferred to as bandwidth adaptation.

NR defines bandwidth parts (BWPs) to support UEs not capable ofreceiving the full carrier bandwidth and to support bandwidthadaptation. In an example, a BWP may be defined by a subset ofcontiguous RBs on a carrier. A UE may be configured (e.g., via RRClayer) with one or more downlink BWPs and one or more uplink BWPs perserving cell (e.g., up to four downlink BWPs and up to four uplink BWPsper serving cell). At a given time, one or more of the configured BWPsfor a serving cell may be active. These one or more BWPs may be referredto as active BWPs of the serving cell. When a serving cell is configuredwith a secondary uplink carrier, the serving cell may have one or morefirst active BWPs in the uplink carrier and one or more second activeBWPs in the secondary uplink carrier.

For unpaired spectra, a downlink BWP from a set of configured downlinkBWPs may be linked with an uplink BWP from a set of configured uplinkBWPs if a downlink BWP index of the downlink BWP and an uplink BWP indexof the uplink BWP are the same. For unpaired spectra, a UE may expectthat a center frequency for a downlink BWP is the same as a centerfrequency for an uplink BWP.

For a downlink BWP in a set of configured downlink BWPs on a primarycell (PCell), a base station may configure a UE with one or more controlresource sets (CORESETs) for at least one search space. A search spaceis a set of locations in the time and frequency domains where the UE mayfind control information. The search space may be a UE-specific searchspace or a common search space (potentially usable by a plurality ofUEs). For example, a base station may configure a UE with a commonsearch space, on a PCell or on a primary secondary cell (PSCell), in anactive downlink BWP.

For an uplink BWP in a set of configured uplink BWPs, a BS may configurea UE with one or more resource sets for one or more PUCCH transmissions.A UE may receive downlink receptions (e.g., PDCCH or PDSCH) in adownlink BWP according to a configured numerology (e.g., subcarrierspacing and cyclic prefix duration) for the downlink BWP. The UE maytransmit uplink transmissions (e.g., PUCCH or PUSCH) in an uplink BWPaccording to a configured numerology (e.g., subcarrier spacing andcyclic prefix length for the uplink BWP).

One or more BWP indicator fields may be provided in Downlink ControlInformation (DCI). A value of a BWP indicator field may indicate whichBWP in a set of configured BWPs is an active downlink BWP for one ormore downlink receptions. The value of the one or more BWP indicatorfields may indicate an active uplink BWP for one or more uplinktransmissions.

A base station may semi-statically configure a UE with a defaultdownlink BWP within a set of configured downlink BWPs associated with aPCell. If the base station does not provide the default downlink BWP tothe UE, the default downlink BWP may be an initial active downlink BWP.The UE may determine which BWP is the initial active downlink BWP basedon a CORESET configuration obtained using the PBCH.

A base station may configure a UE with a BWP inactivity timer value fora PCell. The UE may start or restart a BWP inactivity timer at anyappropriate time. For example, the UE may start or restart the BWPinactivity timer (a) when the UE detects a DCI indicating an activedownlink BWP other than a default downlink BWP for a paired spectraoperation; or (b) when a UE detects a DCI indicating an active downlinkBWP or active uplink BWP other than a default downlink BWP or uplink BWPfor an unpaired spectra operation. If the UE does not detect DCI duringan interval of time (e.g., 1 ms or 0.5 ms), the UE may run the BWPinactivity timer toward expiration (for example, increment from zero tothe BWP inactivity timer value, or decrement from the BWP inactivitytimer value to zero). When the BWP inactivity timer expires, the UE mayswitch from the active downlink BWP to the default downlink BWP.

In an example, a base station may semi-statically configure a UE withone or more BWPs. A UE may switch an active BWP from a first BWP to asecond BWP in response to receiving a DCI indicating the second BWP asan active BWP and/or in response to an expiry of the BWP inactivitytimer (e.g., if the second BWP is the default BWP).

Downlink and uplink BWP switching (where BWP switching refers toswitching from a currently active BWP to a not currently active BWP) maybe performed independently in paired spectra. In unpaired spectra,downlink and uplink BWP switching may be performed simultaneously.Switching between configured BWPs may occur based on RRC signaling, DCI,expiration of a BWP inactivity timer, and/or an initiation of randomaccess.

FIG. 9 illustrates an example of bandwidth adaptation using threeconfigured BWPs for an NR carrier. A UE configured with the three BWPsmay switch from one BWP to another BWP at a switching point. In theexample illustrated in FIG. 9 , the BWPs include: a BWP 902 with abandwidth of 40 MHz and a subcarrier spacing of 15 kHz; a BWP 904 with abandwidth of 10 MHz and a subcarrier spacing of 15 kHz; and a BWP 906with a bandwidth of 20 MHz and a subcarrier spacing of 60 kHz. The BWP902 may be an initial active BWP, and the BWP 904 may be a default BWP.The UE may switch between BWPs at switching points. In the example ofFIG. 9 , the UE may switch from the BWP 902 to the BWP 904 at aswitching point 908. The switching at the switching point 908 may occurfor any suitable reason, for example, in response to an expiry of a BWPinactivity timer (indicating switching to the default BWP) and/or inresponse to receiving a DCI indicating BWP 904 as the active BWP. The UEmay switch at a switching point 910 from active BWP 904 to BWP 906 inresponse receiving a DCI indicating BWP 906 as the active BWP. The UEmay switch at a switching point 912 from active BWP 906 to BWP 904 inresponse to an expiry of a BWP inactivity timer and/or in responsereceiving a DCI indicating BWP 904 as the active BWP. The UE may switchat a switching point 914 from active BWP 904 to BWP 902 in responsereceiving a DCI indicating BWP 902 as the active BWP.

If a UE is configured for a secondary cell with a default downlink BWPin a set of configured downlink BWPs and a timer value, UE proceduresfor switching BWPs on a secondary cell may be the same/similar as thoseon a primary cell. For example, the UE may use the timer value and thedefault downlink BWP for the secondary cell in the same/similar manneras the UE would use these values for a primary cell.

To provide for greater data rates, two or more carriers can beaggregated and simultaneously transmitted to/from the same UE usingcarrier aggregation (CA). The aggregated carriers in CA may be referredto as component carriers (CCs). When CA is used, there are a number ofserving cells for the UE, one for a CC. The CCs may have threeconfigurations in the frequency domain.

FIG. 10A illustrates the three CA configurations with two CCs. In theintraband, contiguous configuration 1002, the two CCs are aggregated inthe same frequency band (frequency band A) and are located directlyadjacent to each other within the frequency band. In the intraband,non-contiguous configuration 1004, the two CCs are aggregated in thesame frequency band (frequency band A) and are separated in thefrequency band by a gap. In the interband configuration 1006, the twoCCs are located in frequency bands (frequency band A and frequency bandB).

In an example, up to 32 CCs may be aggregated. The aggregated CCs mayhave the same or different bandwidths, subcarrier spacing, and/orduplexing schemes (TDD or FDD). A serving cell for a UE using CA mayhave a downlink CC. For FDD, one or more uplink CCs may be optionallyconfigured for a serving cell. The ability to aggregate more downlinkcarriers than uplink carriers may be useful, for example, when the UEhas more data traffic in the downlink than in the uplink.

When CA is used, one of the aggregated cells for a UE may be referred toas a primary cell (PCell). The PCell may be the serving cell that the UEinitially connects to at RRC connection establishment, reestablishment,and/or handover. The PCell may provide the UE with NAS mobilityinformation and the security input. UEs may have different PCells. Inthe downlink, the carrier corresponding to the PCell may be referred toas the downlink primary CC (DL PCC). In the uplink, the carriercorresponding to the PCell may be referred to as the uplink primary CC(UL PCC). The other aggregated cells for the UE may be referred to assecondary cells (SCells). In an example, the SCells may be configuredafter the PCell is configured for the UE. For example, an SCell may beconfigured through an RRC Connection Reconfiguration procedure. In thedownlink, the carrier corresponding to an SCell may be referred to as adownlink secondary CC (DL SCC). In the uplink, the carrier correspondingto the SCell may be referred to as the uplink secondary CC (UL SCC).

Configured SCells for a UE may be activated and deactivated based on,for example, traffic and channel conditions. Deactivation of an SCellmay mean that PDCCH and PDSCH reception on the SCell is stopped andPUSCH, SRS, and CQI transmissions on the SCell are stopped. ConfiguredSCells may be activated and deactivated using a MAC CE with respect toFIG. 4B. For example, a MAC CE may use a bitmap (e.g., one bit perSCell) to indicate which SCells (e.g., in a subset of configured SCells)for the UE are activated or deactivated. Configured SCells may bedeactivated in response to an expiration of an SCell deactivation timer(e.g., one SCell deactivation timer per SCell).

Downlink control information, such as scheduling assignments andscheduling grants, for a cell may be transmitted on the cellcorresponding to the assignments and grants, which is known asself-scheduling. The DCI for the cell may be transmitted on anothercell, which is known as cross-carrier scheduling. Uplink controlinformation (e.g., HARQ acknowledgments and channel state feedback, suchas CQI, PMI, and/or RI) for aggregated cells may be transmitted on thePUCCH of the PCell. For a larger number of aggregated downlink CCs, thePUCCH of the PCell may become overloaded. Cells may be divided intomultiple PUCCH groups.

FIG. 10B illustrates an example of how aggregated cells may beconfigured into one or more PUCCH groups. A PUCCH group 1010 and a PUCCHgroup 1050 may include one or more downlink CCs, respectively. In theexample of FIG. 10B, the PUCCH group 1010 includes three downlink CCs: aPCell 1011, an SCell 1012, and an SCell 1013. The PUCCH group 1050includes three downlink CCs in the present example: a PCell 1051, anSCell 1052, and an SCell 1053. One or more uplink CCs may be configuredas a PCell 1021, an SCell 1022, and an SCell 1023. One or more otheruplink CCs may be configured as a primary SCell (PSCell) 1061, an SCell1062, and an SCell 1063. Uplink control information (UCI) related to thedownlink CCs of the PUCCH group 1010, shown as UCI 1031, UCI 1032, andUCI 1033, may be transmitted in the uplink of the PCell 1021. Uplinkcontrol information (UCI) related to the downlink CCs of the PUCCH group1050, shown as UCI 1071, UCI 1072, and UCI 1073, may be transmitted inthe uplink of the PSCell 1061. In an example, if the aggregated cellsdepicted in FIG. 10B were not divided into the PUCCH group 1010 and thePUCCH group 1050, a single uplink PCell to transmit UCI relating to thedownlink CCs, and the PCell may become overloaded. By dividingtransmissions of UCI between the PCell 1021 and the PSCell 1061,overloading may be prevented.

A cell, comprising a downlink carrier and optionally an uplink carrier,may be assigned with a physical cell ID and a cell index. The physicalcell ID or the cell index may identify a downlink carrier and/or anuplink carrier of the cell, for example, depending on the context inwhich the physical cell ID is used. A physical cell ID may be determinedusing a synchronization signal transmitted on a downlink componentcarrier. A cell index may be determined using RRC messages. In thedisclosure, a physical cell ID may be referred to as a carrier ID, and acell index may be referred to as a carrier index. For example, when thedisclosure refers to a first physical cell ID for a first downlinkcarrier, the disclosure may mean the first physical cell ID is for acell comprising the first downlink carrier. The same/similar concept mayapply to, for example, a carrier activation. When the disclosureindicates that a first carrier is activated, the specification may meanthat a cell comprising the first carrier is activated.

In CA, a multi-carrier nature of a PHY may be exposed to a MAC. In anexample, a HARQ entity may operate on a serving cell. A transport blockmay be generated per assignment/grant per serving cell. A transportblock and potential HARQ retransmissions of the transport block may bemapped to a serving cell.

In the downlink, a base station may transmit (e.g., unicast, multicast,and/or broadcast) one or more Reference Signals (RSs) to a UE (e.g.,PSS, SSS, CSI-RS, DMRS, and/or PT-RS, as shown in FIG. 5A). In theuplink, the UE may transmit one or more RSs to the base station (e.g.,DMRS, PT-RS, and/or SRS, as shown in FIG. 5B). The PSS and the SSS maybe transmitted by the base station and used by the UE to synchronize theUE to the base station. The PSS and the SSS may be provided in asynchronization signal (SS)/physical broadcast channel (PBCH) block thatincludes the PSS, the SSS, and the PBCH. The base station mayperiodically transmit a burst of SS/PBCH blocks.

FIG. 11A illustrates an example of an SS/PBCH block's structure andlocation. A burst of SS/PBCH blocks may include one or more SS/PBCHblocks (e.g., 4 SS/PBCH blocks, as shown in FIG. 11A). Bursts may betransmitted periodically (e.g., every 2 frames or 20 ms). A burst may berestricted to a half-frame (e.g., a first half-frame having a durationof 5 ms). It will be understood that FIG. 11A is an example, and thatthese parameters (number of SS/PBCH blocks per burst, periodicity ofbursts, position of burst within the frame) may be configured based on,for example: a carrier frequency of a cell in which the SS/PBCH block istransmitted; a numerology or subcarrier spacing of the cell; aconfiguration by the network (e.g., using RRC signaling); or any othersuitable factor. In an example, the UE may assume a subcarrier spacingfor the SS/PBCH block based on the carrier frequency being monitored,unless the radio network configured the UE to assume a differentsubcarrier spacing.

The SS/PBCH block may span one or more OFDM symbols in the time domain(e.g., 4 OFDM symbols, as shown in the example of FIG. 11A) and may spanone or more subcarriers in the frequency domain (e.g., 240 contiguoussubcarriers). The PSS, the SSS, and the PBCH may have a common centerfrequency. The PSS may be transmitted first and may span, for example, 1OFDM symbol and 127 subcarriers. The SSS may be transmitted after thePSS (e.g., two symbols later) and may span 1 OFDM symbol and 127subcarriers. The PBCH may be transmitted after the PSS (e.g., across thenext 3 OFDM symbols) and may span 240 subcarriers.

The location of the SS/PBCH block in the time and frequency domains maynot be known to the UE (e.g., if the UE is searching for the cell). Tofind and select the cell, the UE may monitor a carrier for the PSS. Forexample, the UE may monitor a frequency location within the carrier. Ifthe PSS is not found after a certain duration (e.g., 20 ms), the UE maysearch for the PSS at a different frequency location within the carrier,as indicated by a synchronization raster. If the PSS is found at alocation in the time and frequency domains, the UE may determine, basedon a known structure of the SS/PBCH block, the locations of the SSS andthe PBCH, respectively. The SS/PBCH block may be a cell-defining SSblock (CD-SSB). In an example, a primary cell may be associated with aCD-SSB. The CD-SSB may be located on a synchronization raster. In anexample, a cell selection/search and/or reselection may be based on theCD-SSB.

The SS/PBCH block may be used by the UE to determine one or moreparameters of the cell. For example, the UE may determine a physicalcell identifier (PCI) of the cell based on the sequences of the PSS andthe SSS, respectively. The UE may determine a location of a frameboundary of the cell based on the location of the SS/PBCH block. Forexample, the SS/PBCH block may indicate that it has been transmitted inaccordance with a transmission pattern, wherein a SS/PBCH block in thetransmission pattern is a known distance from the frame boundary.

The PBCH may use a QPSK modulation and may use forward error correction(FEC). The FEC may use polar coding. One or more symbols spanned by thePBCH may carry one or more DMRSs for demodulation of the PBCH. The PBCHmay include an indication of a current system frame number (SFN) of thecell and/or a SS/PBCH block timing index. These parameters mayfacilitate time synchronization of the UE to the base station. The PBCHmay include a master information block (MIB) used to provide the UE withone or more parameters. The MIB may be used by the UE to locateremaining minimum system information (RMSI) associated with the cell.The RMSI may include a System Information Block Type 1 (SIB1). The SIB1may contain information needed by the UE to access the cell. The UE mayuse one or more parameters of the MIB to monitor PDCCH, which may beused to schedule PDSCH. The PDSCH may include the SIB1. The SIB1 may bedecoded using parameters provided in the MIB. The PBCH may indicate anabsence of SIB1. Based on the PBCH indicating the absence of SIB1, theUE may be pointed to a frequency. The UE may search for an SS/PBCH blockat the frequency to which the UE is pointed.

The UE may assume that one or more SS/PBCH blocks transmitted with asame SS/PBCH block index are quasi co-located (QCLed) (e.g., having thesame/similar Doppler spread, Doppler shift, average gain, average delay,and/or spatial Rx parameters). The UE may not assume QCL for SS/PBCHblock transmissions having different SS/PBCH block indices.

SS/PBCH blocks (e.g., those within a half-frame) may be transmitted inspatial directions (e.g., using different beams that span a coveragearea of the cell). In an example, a first SS/PBCH block may betransmitted in a first spatial direction using a first beam, and asecond SS/PBCH block may be transmitted in a second spatial directionusing a second beam.

In an example, within a frequency span of a carrier, a base station maytransmit a plurality of SS/PBCH blocks. In an example, a first PCI of afirst SS/PBCH block of the plurality of SS/PBCH blocks may be differentfrom a second PCI of a second SS/PBCH block of the plurality of SS/PBCHblocks. The PCIs of SS/PBCH blocks transmitted in different frequencylocations may be different or the same.

The CSI-RS may be transmitted by the base station and used by the UE toacquire channel state information (CSI). The base station may configurethe UE with one or more CSI-RSs for channel estimation or any othersuitable purpose. The base station may configure a UE with one or moreof the same/similar CSI-RSs. The UE may measure the one or more CSI-RSs.The UE may estimate a downlink channel state and/or generate a CSIreport based on the measuring of the one or more downlink CSI-RSs. TheUE may provide the CSI report to the base station. The base station mayuse feedback provided by the UE (e.g., the estimated downlink channelstate) to perform link adaptation.

The base station may semi-statically configure the UE with one or moreCSI-RS resource sets. A CSI-RS resource may be associated with alocation in the time and frequency domains and a periodicity. The basestation may selectively activate and/or deactivate a CSI-RS resource.The base station may indicate to the UE that a CSI-RS resource in theCSI-RS resource set is activated and/or deactivated.

The base station may configure the UE to report CSI measurements. Thebase station may configure the UE to provide CSI reports periodically,aperiodically, or semi-persistently. For periodic CSI reporting, the UEmay be configured with a timing and/or periodicity of a plurality of CSIreports. For aperiodic CSI reporting, the base station may request a CSIreport. For example, the base station may command the UE to measure aconfigured CSI-RS resource and provide a CSI report relating to themeasurements. For semi-persistent CSI reporting, the base station mayconfigure the UE to transmit periodically, and selectively activate ordeactivate the periodic reporting. The base station may configure the UEwith a CSI-RS resource set and CSI reports using RRC signaling.

The CSI-RS configuration may comprise one or more parameters indicating,for example, up to 32 antenna ports. The UE may be configured to employthe same OFDM symbols for a downlink CSI-RS and a control resource set(CORESET) when the downlink CSI-RS and CORESET are spatially QCLed andresource elements associated with the downlink CSI-RS are outside of thephysical resource blocks (PRBs) configured for the CORESET. The UE maybe configured to employ the same OFDM symbols for downlink CSI-RS andSS/PBCH blocks when the downlink CSI-RS and SS/PBCH blocks are spatiallyQCLed and resource elements associated with the downlink CSI-RS areoutside of PRBs configured for the SS/PBCH blocks.

Downlink DMRSs may be transmitted by a base station and used by a UE forchannel estimation. For example, the downlink DMRS may be used forcoherent demodulation of one or more downlink physical channels (e.g.,PDSCH). An NR network may support one or more variable and/orconfigurable DMRS patterns for data demodulation. At least one downlinkDMRS configuration may support a front-loaded DMRS pattern. Afront-loaded DMRS may be mapped over one or more OFDM symbols (e.g., oneor two adjacent OFDM symbols). A base station may semi-staticallyconfigure the UE with a number (e.g. a maximum number) of front-loadedDMRSsymbols for PDSCH. A DMRS configuration may support one or more DMRSports. For example, for single user-MIMO, a DMRS configuration maysupport up to eight orthogonal downlink DMRS ports per UE. Formultiuser-MIMO, a DMRS configuration may support up to 4 orthogonaldownlink DMRS ports per UE. A radio network may support (e.g., at leastfor CP-OFDM) a common DMRS structure for downlink and uplink, wherein aDMRS location, a DMRS pattern, and/or a scrambling sequence may be thesame or different. The base station may transmit a downlink DMRS and acorresponding PDSCH using the same precoding matrix. The UE may use theone or more downlink DMRSs for coherent demodulation/channel estimationof the PDSCH.

In an example, a transmitter (e.g., a base station) may use a precodermatrices for a part of a transmission bandwidth. For example, thetransmitter may use a first precoder matrix for a first bandwidth and asecond precoder matrix for a second bandwidth. The first precoder matrixand the second precoder matrix may be different based on the firstbandwidth being different from the second bandwidth. The UE may assumethat a same precoding matrix is used across a set of PRBs. The set ofPRBs may be denoted as a precoding resource block group (PRG).

A PDSCH may comprise one or more layers. The UE may assume that at leastone symbol with DMRS is present on a layer of the one or more layers ofthe PDSCH. A higher layer may configure up to 3 DMRSs for the PDSCH.

Downlink PT-RS may be transmitted by a base station and used by a UE forphase-noise compensation. Whether a downlink PT-RS is present or not maydepend on an RRC configuration. The presence and/or pattern of thedownlink PT-RS may be configured on a UE-specific basis using acombination of RRC signaling and/or an association with one or moreparameters employed for other purposes (e.g., modulation and codingscheme (MCS)), which may be indicated by DCI. When configured, a dynamicpresence of a downlink PT-RS may be associated with one or more DCIparameters comprising at least MCS. An NR network may support aplurality of PT-RS densities defined in the time and/or frequencydomains. When present, a frequency domain density may be associated withat least one configuration of a scheduled bandwidth. The UE may assume asame precoding for a DMRS port and a PT-RS port. A number of PT-RS portsmay be fewer than a number of DMRS ports in a scheduled resource.Downlink PT-RS may be confined in the scheduled time/frequency durationfor the UE. Downlink PT-RS may be transmitted on symbols to facilitatephase tracking at the receiver.

The UE may transmit an uplink DMRS to a base station for channelestimation. For example, the base station may use the uplink DMRS forcoherent demodulation of one or more uplink physical channels. Forexample, the UE may transmit an uplink DMRS with a PUSCH and/or a PUCCH.The uplink DM-RS may span a range of frequencies that is similar to arange of frequencies associated with the corresponding physical channel.The base station may configure the UE with one or more uplink DMRSconfigurations. At least one DMRS configuration may support afront-loaded DMRS pattern. The front-loaded DMRS may be mapped over oneor more OFDM symbols (e.g., one or two adjacent OFDM symbols). One ormore uplink DMRSs may be configured to transmit at one or more symbolsof a PUSCH and/or a PUCCH. The base station may semi-staticallyconfigure the UE with a number (e.g. maximum number) of front-loadedDMRS symbols for the PUSCH and/or the PUCCH, which the UE may use toschedule a single-symbol DMRS and/or a double-symbol DMRS. An NR networkmay support (e.g., for cyclic prefix orthogonal frequency divisionmultiplexing (CP-OFDM)) a common DMRS structure for downlink and uplink,wherein a DMRS location, a DMRS pattern, and/or a scrambling sequencefor the DMRS may be the same or different.

A PUSCH may comprise one or more layers, and the UE may transmit atleast one symbol with DMRS present on a layer of the one or more layersof the PUSCH. In an example, a higher layer may configure up to threeDMRSs for the PUSCH.

Uplink PT-RS (which may be used by a base station for phase trackingand/or phase-noise compensation) may or may not be present depending onan RRC configuration of the UE. The presence and/or pattern of uplinkPT-RS may be configured on a UE-specific basis by a combination of RRCsignaling and/or one or more parameters employed for other purposes(e.g., Modulation and Coding Scheme (MCS)), which may be indicated byDCI. When configured, a dynamic presence of uplink PT-RS may beassociated with one or more DCI parameters comprising at least MCS. Aradio network may support a plurality of uplink PT-RS densities definedin time/frequency domain. When present, a frequency domain density maybe associated with at least one configuration of a scheduled bandwidth.The UE may assume a same precoding for a DMRS port and a PT-RS port. Anumber of PT-RS ports may be fewer than a number of DMRS ports in ascheduled resource. For example, uplink PT-RS may be confined in thescheduled time/frequency duration for the UE.

SRS may be transmitted by a UE to a base station for channel stateestimation to support uplink channel dependent scheduling and/or linkadaptation. SRS transmitted by the UE may allow a base station toestimate an uplink channel state at one or more frequencies. A schedulerat the base station may employ the estimated uplink channel state toassign one or more resource blocks for an uplink PUSCH transmission fromthe UE. The base station may semi-statically configure the UE with oneor more SRS resource sets. For an SRS resource set, the base station mayconfigure the UE with one or more SRS resources. An SRS resource setapplicability may be configured by a higher layer (e.g., RRC) parameter.For example, when a higher layer parameter indicates beam management, anSRS resource in a SRS resource set of the one or more SRS resource sets(e.g., with the same/similar time domain behavior, periodic, aperiodic,and/or the like) may be transmitted at a time instant (e.g.,simultaneously). The UE may transmit one or more SRS resources in SRSresource sets. An NR network may support aperiodic, periodic and/orsemi-persistent SRS transmissions. The UE may transmit SRS resourcesbased on one or more trigger types, wherein the one or more triggertypes may comprise higher layer signaling (e.g., RRC) and/or one or moreDCI formats. In an example, at least one DCI format may be employed forthe UE to select at least one of one or more configured SRS resourcesets. An SRS trigger type 0 may refer to an SRS triggered based on ahigher layer signaling. An SRS trigger type 1 may refer to an SRStriggered based on one or more DCI formats. In an example, when PUSCHand SRS are transmitted in a same slot, the UE may be configured totransmit SRS after a transmission of a PUSCH and a corresponding uplinkDMRS.

The base station may semi-statically configure the UE with one or moreSRS configuration parameters indicating at least one of following: a SRSresource configuration identifier; a number of SRS ports; time domainbehavior of an SRS resource configuration (e.g., an indication ofperiodic, semi-persistent, or aperiodic SRS); slot, mini-slot, and/orsubframe level periodicity; offset for a periodic and/or an aperiodicSRS resource; a number of OFDM symbols in an SRS resource; a startingOFDM symbol of an SRS resource; an SRS bandwidth; a frequency hoppingbandwidth; a cyclic shift; and/or an SRS sequence ID.

An antenna port is defined such that the channel over which a symbol onthe antenna port is conveyed can be inferred from the channel over whichanother symbol on the same antenna port is conveyed. If a first symboland a second symbol are transmitted on the same antenna port, thereceiver may infer the channel (e.g., fading gain, multipath delay,and/or the like) for conveying the second symbol on the antenna port,from the channel for conveying the first symbol on the antenna port. Afirst antenna port and a second antenna port may be referred to as quasico-located (QCLed) if one or more large-scale properties of the channelover which a first symbol on the first antenna port is conveyed may beinferred from the channel over which a second symbol on a second antennaport is conveyed. The one or more large-scale properties may comprise atleast one of: a delay spread; a Doppler spread; a Doppler shift; anaverage gain; an average delay; and/or spatial Receiving (Rx)parameters.

Channels that use beamforming require beam management. Beam managementmay comprise beam measurement, beam selection, and beam indication. Abeam may be associated with one or more reference signals. For example,a beam may be identified by one or more beamformed reference signals.The UE may perform downlink beam measurement based on downlink referencesignals (e.g., a channel state information reference signal (CSI-RS))and generate a beam measurement report. The UE may perform the downlinkbeam measurement procedure after an RRC connection is set up with a basestation.

FIG. 11B illustrates an example of channel state information referencesignals (CSI-RSs) that are mapped in the time and frequency domains. Asquare shown in FIG. 11B may span a resource block (RB) within abandwidth of a cell. A base station may transmit one or more RRCmessages comprising CSI-RS resource configuration parameters indicatingone or more CSI-RSs. One or more of the following parameters may beconfigured by higher layer signaling (e.g., RRC and/or MAC signaling)for a CSI-RS resource configuration: a CSI-RS resource configurationidentity, a number of CSI-RS ports, a CSI-RS configuration (e.g., symboland resource element (RE) locations in a subframe), a CSI-RS subframeconfiguration (e.g., subframe location, offset, and periodicity in aradio frame), a CSI-RS power parameter, a CSI-RS sequence parameter, acode division multiplexing (CDM) type parameter, a frequency density, atransmission comb, quasi co-location (QCL) parameters (e.g.,QCL-scramblingidentity, crs-portscount, mbsfn-subframeconfiglist,csi-rs-configZPid, qcl-csi-rs-configNZPid), and/or other radio resourceparameters.

The three beams illustrated in FIG. 11B may be configured for a UE in aUE-specific configuration. Three beams are illustrated in FIG. 11B (beam#1, beam #2, and beam #3), more or fewer beams may be configured. Beam#1 may be allocated with CSI-RS 1101 that may be transmitted in one ormore subcarriers in an RB of a first symbol. Beam #2 may be allocatedwith CSI-RS 1102 that may be transmitted in one or more subcarriers inan RB of a second symbol. Beam #3 may be allocated with CSI-RS 1103 thatmay be transmitted in one or more subcarriers in an RB of a thirdsymbol. By using frequency division multiplexing (FDM), a base stationmay use other subcarriers in a same RB (for example, those that are notused to transmit CSI-RS 1101) to transmit another CSI-RS associated witha beam for another UE. By using time domain multiplexing (TDM), beamsused for the UE may be configured such that beams for the UE use symbolsfrom beams of other UEs.

CSI-RSs such as those illustrated in FIG. 11B (e.g., CSI-RS 1101, 1102,1103) may be transmitted by the base station and used by the UE for oneor more measurements. For example, the UE may measure a reference signalreceived power (RSRP) of configured CSI-RS resources. The base stationmay configure the UE with a reporting configuration and the UE mayreport the RSRP measurements to a network (for example, via one or morebase stations) based on the reporting configuration. In an example, thebase station may determine, based on the reported measurement results,one or more transmission configuration indication (TCI) statescomprising a number of reference signals. In an example, the basestation may indicate one or more TCI states to the UE (e.g., via RRCsignaling, a MAC CE, and/or a DCI). The UE may receive a downlinktransmission with a receive (Rx) beam determined based on the one ormore TCI states. In an example, the UE may or may not have a capabilityof beam correspondence. If the UE has the capability of beamcorrespondence, the UE may determine a spatial domain filter of atransmit (Tx) beam based on a spatial domain filter of the correspondingRx beam. If the UE does not have the capability of beam correspondence,the UE may perform an uplink beam selection procedure to determine thespatial domain filter of the Tx beam. The UE may perform the uplink beamselection procedure based on one or more sounding reference signal (SRS)resources configured to the UE by the base station. The base station mayselect and indicate uplink beams for the UE based on measurements of theone or more SRS resources transmitted by the UE.

In a beam management procedure, a UE may assess (e.g., measure) achannel quality of one or more beam pair links, a beam pair linkcomprising a transmitting beam transmitted by a base station and areceiving beam received by the UE. Based on the assessment, the UE maytransmit a beam measurement report indicating one or more beam pairquality parameters comprising, e.g., one or more beam identifications(e.g., a beam index, a reference signal index, or the like), RSRP, aprecoding matrix indicator (PMI), a channel quality indicator (CQI),and/or a rank indicator (RI).

FIG. 12A illustrates examples of three downlink beam managementprocedures: P1, P2, and P3. Procedure P1 may enable a UE measurement ontransmit (Tx) beams of a transmission reception point (TRP) (or multipleTRPs), e.g., to support a selection of one or more base station Tx beamsand/or UE Rx beams (shown as ovals in the top row and bottom row,respectively, of P1). Beamforming at a TRP may comprise a Tx beam sweepfor a set of beams (shown, in the top rows of P1 and P2, as ovalsrotated in a counter-clockwise direction indicated by the dashed arrow).Beamforming at a UE may comprise an Rx beam sweep for a set of beams(shown, in the bottom rows of P1 and P3, as ovals rotated in a clockwisedirection indicated by the dashed arrow). Procedure P2 may be used toenable a UE measurement on Tx beams of a TRP (shown, in the top row ofP2, as ovals rotated in a counter-clockwise direction indicated by thedashed arrow). The UE and/or the base station may perform procedure P2using a smaller set of beams than is used in procedure P1, or usingnarrower beams than the beams used in procedure P1. This may be referredto as beam refinement. The UE may perform procedure P3 for Rx beamdetermination by using the same Tx beam at the base station and sweepingan Rx beam at the UE.

FIG. 12B illustrates examples of three uplink beam managementprocedures: U1, U2, and U3. Procedure U1 may be used to enable a basestation to perform a measurement on Tx beams of a UE, e.g., to support aselection of one or more UE Tx beams and/or base station Rx beams (shownas ovals in the top row and bottom row, respectively, of U1).Beamforming at the UE may include, e.g., a Tx beam sweep from a set ofbeams (shown in the bottom rows of U1 and U3 as ovals rotated in aclockwise direction indicated by the dashed arrow). Beamforming at thebase station may include, e.g., an Rx beam sweep from a set of beams(shown, in the top rows of U1 and U2, as ovals rotated in acounter-clockwise direction indicated by the dashed arrow). Procedure U2may be used to enable the base station to adjust its Rx beam when the UEuses a fixed Tx beam. The UE and/or the base station may performprocedure U2 using a smaller set of beams than is used in procedure P1,or using narrower beams than the beams used in procedure P1. This may bereferred to as beam refinement The UE may perform procedure U3 to adjustits Tx beam when the base station uses a fixed Rx beam.

A UE may initiate a beam failure recovery (BFR) procedure based ondetecting a beam failure. The UE may transmit a BFR request (e.g., apreamble, a UCI, an SR, a MAC CE, and/or the like) based on theinitiating of the BFR procedure. The UE may detect the beam failurebased on a determination that a quality of beam pair link(s) of anassociated control channel is unsatisfactory (e.g., having an error ratehigher than an error rate threshold, a received signal power lower thana received signal power threshold, an expiration of a timer, and/or thelike).

The UE may measure a quality of a beam pair link using one or morereference signals (RSs) comprising one or more SS/PBCH blocks, one ormore CSI-RS resources, and/or one or more demodulation reference signals(DMRSs). A quality of the beam pair link may be based on one or more ofa block error rate (BLER), an RSRP value, a signal to interference plusnoise ratio (SINR) value, a reference signal received quality (RSRQ)value, and/or a CSI value measured on RS resources. The base station mayindicate that an RS resource is quasi co-located (QCLed) with one ormore DM-RSs of a channel (e.g., a control channel, a shared datachannel, and/or the like). The RS resource and the one or more DMRSs ofthe channel may be QCLed when the channel characteristics (e.g., Dopplershift, Doppler spread, average delay, delay spread, spatial Rxparameter, fading, and/or the like) from a transmission via the RSresource to the UE are similar or the same as the channelcharacteristics from a transmission via the channel to the UE.

A network (e.g., a gNB and/or an ng-eNB of a network) and/or the UE mayinitiate a random access procedure. A UE in an RRC_IDLE state and/or anRRC_INACTIVE state may initiate the random access procedure to request aconnection setup to a network. The UE may initiate the random accessprocedure from an RRC_CONNECTED state. The UE may initiate the randomaccess procedure to request uplink resources (e.g., for uplinktransmission of an SR when there is no PUCCH resource available) and/oracquire uplink timing (e.g., when uplink synchronization status isnon-synchronized). The UE may initiate the random access procedure torequest one or more system information blocks (SIBs) (e.g., other systeminformation such as SIB2, SIB3, and/or the like). The UE may initiatethe random access procedure for a beam failure recovery request. Anetwork may initiate a random access procedure for a handover and/or forestablishing time alignment for an SCell addition.

FIG. 13A illustrates a four-step contention-based random accessprocedure. Prior to initiation of the procedure, a base station maytransmit a configuration message 1310 to the UE. The procedureillustrated in FIG. 13A comprises transmission of four messages: a Msg 11311, a Msg 2 1312, a Msg 3 1313, and a Msg 4 1314. The Msg 1 1311 mayinclude and/or be referred to as a preamble (or a random accesspreamble). The Msg 2 1312 may include and/or be referred to as a randomaccess response (RAR).

The configuration message 1310 may be transmitted, for example, usingone or more RRC messages. The one or more RRC messages may indicate oneor more random access channel (RACH) parameters to the UE. The one ormore RACH parameters may comprise at least one of following: generalparameters for one or more random access procedures (e.g.,RACH-configGeneral); cell-specific parameters (e.g., RACH-ConfigCommon);and/or dedicated parameters (e.g., RACH-configDedicated). The basestation may broadcast or multicast the one or more RRC messages to oneor more UEs. The one or more RRC messages may be UE-specific (e.g.,dedicated RRC messages transmitted to a UE in an RRC_CONNECTED stateand/or in an RRC_INACTIVE state). The UE may determine, based on the oneor more RACH parameters, a time-frequency resource and/or an uplinktransmit power for transmission of the Msg 1 1311 and/or the Msg 3 1313.Based on the one or more RACH parameters, the UE may determine areception timing and a downlink channel for receiving the Msg 2 1312 andthe Msg 4 1314.

The one or more RACH parameters provided in the configuration message1310 may indicate one or more Physical RACH (PRACH) occasions availablefor transmission of the Msg 1 1311. The one or more PRACH occasions maybe predefined. The one or more RACH parameters may indicate one or moreavailable sets of one or more PRACH occasions (e.g., prach-Configlndex).The one or more RACH parameters may indicate an association between (a)one or more PRACH occasions and (b) one or more reference signals. Theone or more RACH parameters may indicate an association between (a) oneor more preambles and (b) one or more reference signals. The one or morereference signals may be SS/PBCH blocks and/or CSI-RSs. For example, theone or more RACH parameters may indicate a number of SS/PBCH blocksmapped to a PRACH occasion and/or a number of preambles mapped to aSS/PBCH blocks.

The one or more RACH parameters provided in the configuration message1310 may be used to determine an uplink transmit power of Msg 1 1311and/or Msg 3 1313. For example, the one or more RACH parameters mayindicate a reference power for a preamble transmission (e.g., a receivedtarget power and/or an initial power of the preamble transmission).There may be one or more power offsets indicated by the one or more RACHparameters. For example, the one or more RACH parameters may indicate: apower ramping step; a power offset between SSB and CSI-RS; a poweroffset between transmissions of the Msg 1 1311 and the Msg 3 1313;and/or a power offset value between preamble groups. The one or moreRACH parameters may indicate one or more thresholds based on which theUE may determine at least one reference signal (e.g., an SSB and/orCSI-RS) and/or an uplink carrier (e.g., a normal uplink (NUL) carrierand/or a supplemental uplink (SUL) carrier).

The Msg 1 1311 may include one or more preamble transmissions (e.g., apreamble transmission and one or more preamble retransmissions). An RRCmessage may be used to configure one or more preamble groups (e.g.,group A and/or group B). A preamble group may comprise one or morepreambles. The UE may determine the preamble group based on a pathlossmeasurement and/or a size of the Msg 3 1313. The UE may measure an RSRPof one or more reference signals (e.g., SSBs and/or CSI-RSs) anddetermine at least one reference signal having an RSRP above an RSRPthreshold (e.g., rsrp-ThresholdSSB and/or rsrp-ThresholdCSI-RS). The UEmay select at least one preamble associated with the one or morereference signals and/or a selected preamble group, for example, if theassociation between the one or more preambles and the at least onereference signal is configured by an RRC message.

The UE may determine the preamble based on the one or more RACHparameters provided in the configuration message 1310. For example, theUE may determine the preamble based on a pathloss measurement, an RSRPmeasurement, and/or a size of the Msg 3 1313. As another example, theone or more RACH parameters may indicate: a preamble format; a maximumnumber of preamble transmissions; and/or one or more thresholds fordetermining one or more preamble groups (e.g., group A and group B). Abase station may use the one or more RACH parameters to configure the UEwith an association between one or more preambles and one or morereference signals (e.g., SSBs and/or CSI-RSs). If the association isconfigured, the UE may determine the preamble to include in Msg 1 1311based on the association. The Msg 1 1311 may be transmitted to the basestation via one or more PRACH occasions. The UE may use one or morereference signals (e.g., SSBs and/or CSI-RSs) for selection of thepreamble and for determining of the PRACH occasion. One or more RACHparameters (e.g., ra-ssb-OccasionMskIndex and/or ra-OccasionList) mayindicate an association between the PRACH occasions and the one or morereference signals.

The UE may perform a preamble retransmission if no response is receivedfollowing a preamble transmission. The UE may increase an uplinktransmit power for the preamble retransmission. The UE may select aninitial preamble transmit power based on a pathloss measurement and/or atarget received preamble power configured by the network. The UE maydetermine to retransmit a preamble and may ramp up the uplink transmitpower. The UE may receive one or more RACH parameters (e.g.,PREAMBLE_POWER_RAMPING_STEP) indicating a ramping step for the preambleretransmission. The ramping step may be an amount of incrementalincrease in uplink transmit power for a retransmission. The UE may rampup the uplink transmit power if the UE determines a reference signal(e.g., SSB and/or CSI-RS) that is the same as a previous preambletransmission. The UE may count a number of preamble transmissions and/orretransmissions (e.g., PREAMBLE_TRANSMISSION_COUNTER). The UE maydetermine that a random access procedure completed unsuccessfully, forexample, if the number of preamble transmissions exceeds a thresholdconfigured by the one or more RACH parameters (e.g., preambleTransMax).

The Msg 2 1312 received by the UE may include an RAR. In some scenarios,the Msg 2 1312 may include multiple RARs corresponding to multiple UEs.The Msg 2 1312 may be received after or in response to the transmittingof the Msg 1 1311. The Msg 2 1312 may be scheduled on the DL-SCH andindicated on a PDCCH using a random access RNTI (RA-RNTI). The Msg 21312 may indicate that the Msg 1 1311 was received by the base station.The Msg 2 1312 may include a time-alignment command that may be used bythe UE to adjust the UE's transmission timing, a scheduling grant fortransmission of the Msg 3 1313, and/or a Temporary Cell RNTI (TC-RNTI).After transmitting a preamble, the UE may start a time window (e.g.,ra-ResponseWindow) to monitor a PDCCH for the Msg 2 1312. The UE maydetermine when to start the time window based on a PRACH occasion thatthe UE uses to transmit the preamble. For example, the UE may start thetime window one or more symbols after a last symbol of the preamble(e.g., at a first PDCCH occasion from an end of a preambletransmission). The one or more symbols may be determined based on anumerology. The PDCCH may be in a common search space (e.g., aType1-PDCCH common search space) configured by an RRC message. The UEmay identify the RAR based on a Radio Network Temporary Identifier(RNTI). RNTIs may be used depending on one or more events initiating therandom access procedure. The UE may use random access RNTI (RA-RNTI).The RA-RNTI may be associated with PRACH occasions in which the UEtransmits a preamble. For example, the UE may determine the RA-RNTIbased on: an OFDM symbol index; a slot index; a frequency domain index;and/or a UL carrier indicator of the PRACH occasions. An example ofRA-RNTI may be as follows:

RA-RNTI=1+s_id+14×t_id+14×80×f_id+14×80×8×ul_carrier_id

where s_id may be an index of a first OFDM symbol of the PRACH occasion(e.g., 0≤s_id<14), t_id may be an index of a first slot of the PRACHoccasion in a system frame (e.g., 0≤t_id<80), f_id may be an index ofthe PRACH occasion in the frequency domain (e.g., 0≤f_id<8), andul_carrier_id may be a UL carrier used for a preamble transmission(e.g., 0 for an NUL carrier, and 1 for an SUL carrier).

The UE may transmit the Msg 3 1313 in response to a successful receptionof the Msg 2 1312 (e.g., using resources identified in the Msg 2 1312).The Msg 3 1313 may be used for contention resolution in, for example,the contention-based random access procedure illustrated in FIG. 13A. Insome scenarios, a plurality of UEs may transmit a same preamble to abase station and the base station may provide an RAR that corresponds toa UE. Collisions may occur if the plurality of UEs interpret the RAR ascorresponding to themselves. Contention resolution (e.g., using the Msg3 1313 and the Msg 4 1314) may be used to increase the likelihood thatthe UE does not incorrectly use an identity of another the UE. Toperform contention resolution, the UE may include a device identifier inthe Msg 3 1313 (e.g., a C-RNTI if assigned, a TC-RNTI included in theMsg 2 1312, and/or any other suitable identifier).

The Msg 4 1314 may be received after or in response to the transmittingof the Msg 3 1313. If a C-RNTI was included in the Msg 3 1313, the basestation will address the UE on the PDCCH using the C-RNTI. If the UE'sunique C-RNTI is detected on the PDCCH, the random access procedure isdetermined to be successfully completed. If a TC-RNTI is included in theMsg 3 1313 (e.g., if the UE is in an RRC_IDLE state or not otherwiseconnected to the base station), Msg 4 1314 will be received using aDL-SCH associated with the TC-RNTI. If a MAC PDU is successfully decodedand a MAC PDU comprises the UE contention resolution identity MAC CEthat matches or otherwise corresponds with the CCCH SDU sent (e.g.,transmitted) in Msg 3 1313, the UE may determine that the contentionresolution is successful and/or the UE may determine that the randomaccess procedure is successfully completed.

The UE may be configured with a supplementary uplink (SUL) carrier and anormal uplink (NUL) carrier. An initial access (e.g., random accessprocedure) may be supported in an uplink carrier. For example, a basestation may configure the UE with two separate RACH configurations: onefor an SUL carrier and the other for an NUL carrier. For random accessin a cell configured with an SUL carrier, the network may indicate whichcarrier to use (NUL or SUL). The UE may determine the SUL carrier, forexample, if a measured quality of one or more reference signals is lowerthan a broadcast threshold. Uplink transmissions of the random accessprocedure (e.g., the Msg 1 1311 and/or the Msg 3 1313) may remain on theselected carrier. The UE may switch an uplink carrier during the randomaccess procedure (e.g., between the Msg 1 1311 and the Msg 3 1313) inone or more cases. For example, the UE may determine and/or switch anuplink carrier for the Msg 1 1311 and/or the Msg 3 1313 based on achannel clear assessment (e.g., a listen-before-talk).

FIG. 13B illustrates a two-step contention-free random access procedure.Similar to the four-step contention-based random access procedureillustrated in FIG. 13A, a base station may, prior to initiation of theprocedure, transmit a configuration message 1320 to the UE. Theconfiguration message 1320 may be analogous in some respects to theconfiguration message 1310. The procedure illustrated in FIG. 13Bcomprises transmission of two messages: a Msg 1 1321 and a Msg 2 1322.The Msg 1 1321 and the Msg 2 1322 may be analogous in some respects tothe Msg 1 1311 and a Msg 2 1312 illustrated in FIG. 13A, respectively.As will be understood from FIGS. 13A and 13B, the contention-free randomaccess procedure may not include messages analogous to the Msg 3 1313and/or the Msg 4 1314.

The contention-free random access procedure illustrated in FIG. 13B maybe initiated for a beam failure recovery, other SI request, SCelladdition, and/or handover. For example, a base station may indicate orassign to the UE the preamble to be used for the Msg 1 1321. The UE mayreceive, from the base station via PDCCH and/or RRC, an indication of apreamble (e.g., ra-PreambleIndex).

After transmitting a preamble, the UE may start a time window (e.g.,ra-ResponseWindow) to monitor a PDCCH for the RAR. In the event of abeam failure recovery request, the base station may configure the UEwith a separate time window and/or a separate PDCCH in a search spaceindicated by an RRC message (e.g., recoverySearchSpaceId). The UE maymonitor for a PDCCH transmission addressed to a Cell RNTI (C-RNTI) onthe search space. In the contention-free random access procedureillustrated in FIG. 13B, the UE may determine that a random accessprocedure successfully completes after or in response to transmission ofMsg 1 1321 and reception of a corresponding Msg 2 1322. The UE maydetermine that a random access procedure successfully completes, forexample, if a PDCCH transmission is addressed to a C-RNTI. The UE maydetermine that a random access procedure successfully completes, forexample, if the UE receives an RAR comprising a preamble identifiercorresponding to a preamble transmitted by the UE and/or the RARcomprises a MAC sub-PDU with the preamble identifier. The UE maydetermine the response as an indication of an acknowledgement for an SIrequest.

FIG. 13C illustrates another two-step random access procedure. Similarto the random access procedures illustrated in FIGS. 13A and 13B, a basestation may, prior to initiation of the procedure, transmit aconfiguration message 1330 to the UE. The configuration message 1330 maybe analogous in some respects to the configuration message 1310 and/orthe configuration message 1320. The procedure illustrated in FIG. 13Ccomprises transmission of two messages: a Msg A 1331 and a Msg B 1332.

Msg A 1331 may be transmitted in an uplink transmission by the UE. Msg A1331 may comprise one or more transmissions of a preamble 1341 and/orone or more transmissions of a transport block 1342. The transport block1342 may comprise contents that are similar and/or equivalent to thecontents of the Msg 3 1313 illustrated in FIG. 13A. The transport block1342 may comprise UCI (e.g., an SR, a HARQ ACK/NACK, and/or the like).The UE may receive the Msg B 1332 after or in response to transmittingthe Msg A 1331. The Msg B 1332 may comprise contents that are similarand/or equivalent to the contents of the Msg 2 1312 (e.g., an RAR)illustrated in FIGS. 13A and 13B and/or the Msg 4 1314 illustrated inFIG. 13A.

The UE may initiate the two-step random access procedure in FIG. 13C forlicensed spectrum and/or unlicensed spectrum. The UE may determine,based on one or more factors, whether to initiate the two-step randomaccess procedure. The one or more factors may be: a radio accesstechnology in use (e.g., LTE, NR, and/or the like); whether the UE hasvalid TA or not; a cell size; the UE's RRC state; a type of spectrum(e.g., licensed vs. unlicensed); and/or any other suitable factors.

The UE may determine, based on two-step RACH parameters included in theconfiguration message 1330, a radio resource and/or an uplink transmitpower for the preamble 1341 and/or the transport block 1342 included inthe Msg A 1331. The RACH parameters may indicate a modulation and codingschemes (MCS), a time-frequency resource, and/or a power control for thepreamble 1341 and/or the transport block 1342. A time-frequency resourcefor transmission of the preamble 1341 (e.g., a PRACH) and atime-frequency resource for transmission of the transport block 1342(e.g., a PUSCH) may be multiplexed using FDM, TDM, and/or CDM. The RACHparameters may enable the UE to determine a reception timing and adownlink channel for monitoring for and/or receiving Msg B 1332.

The transport block 1342 may comprise data (e.g., delay-sensitive data),an identifier of the UE, security information, and/or device information(e.g., an International Mobile Subscriber Identity (IMSI)). The basestation may transmit the Msg B 1332 as a response to the Msg A 1331. TheMsg B 1332 may comprise at least one of following: a preambleidentifier; a timing advance command; a power control command; an uplinkgrant (e.g., a radio resource assignment and/or an MCS); a UE identifierfor contention resolution; and/or an RNTI (e.g., a C-RNTI or a TC-RNTI).The UE may determine that the two-step random access procedure issuccessfully completed if: a preamble identifier in the Msg B 1332 ismatched to a preamble transmitted by the UE; and/or the identifier ofthe UE in Msg B 1332 is matched to the identifier of the UE in the Msg A1331 (e.g., the transport block 1342).

A UE and a base station may exchange control signaling. The controlsignaling may be referred to as L1/L2 control signaling and mayoriginate from the PHY layer (e.g., layer 1) and/or the MAC layer (e.g.,layer 2). The control signaling may comprise downlink control signalingtransmitted from the base station to the UE and/or uplink controlsignaling transmitted from the UE to the base station.

The downlink control signaling may comprise: a downlink schedulingassignment; an uplink scheduling grant indicating uplink radio resourcesand/or a transport format; a slot format information; a preemptionindication; a power control command; and/or any other suitablesignaling. The UE may receive the downlink control signaling in apayload transmitted by the base station on a physical downlink controlchannel (PDCCH). The payload transmitted on the PDCCH may be referred toas downlink control information (DCI). In some scenarios, the PDCCH maybe a group common PDCCH (GC-PDCCH) that is common to a group of UEs.

A base station may attach one or more cyclic redundancy check (CRC)parity bits to a DCI in order to facilitate detection of transmissionerrors. When the DCI is intended for a UE (or a group of the UEs), thebase station may scramble the CRC parity bits with an identifier of theUE (or an identifier of the group of the UEs). Scrambling the CRC paritybits with the identifier may comprise Modulo-2 addition (or an exclusiveOR operation) of the identifier value and the CRC parity bits. Theidentifier may comprise a 16-bit value of a radio network temporaryidentifier (RNTI).

DCIs may be used for different purposes. A purpose may be indicated bythe type of RNTI used to scramble the CRC parity bits. For example, aDCI having CRC parity bits scrambled with a paging RNTI (P-RNTI) mayindicate paging information and/or a system information changenotification. The P-RNTI may be predefined as “FFFE” in hexadecimal. ADCI having CRC parity bits scrambled with a system information RNTI(SI-RNTI) may indicate a broadcast transmission of the systeminformation. The SI-RNTI may be predefined as “FFFF” in hexadecimal. ADCI having CRC parity bits scrambled with a random access RNTI (RA-RNTI)may indicate a random access response (RAR). A DCI having CRC paritybits scrambled with a cell RNTI (C-RNTI) may indicate a dynamicallyscheduled unicast transmission and/or a triggering of PDCCH-orderedrandom access. A DCI having CRC parity bits scrambled with a temporarycell RNTI (TC-RNTI) may indicate a contention resolution (e.g., a Msg 3analogous to the Msg 3 1313 illustrated in FIG. 13A). Other RNTIsconfigured to the UE by a base station may comprise a ConfiguredScheduling RNTI (CS-RNTI), a Transmit Power Control-PUCCH RNTI(TPC-PUCCH-RNTI), a Transmit Power Control-PUSCH RNTI (TPC-PUSCH-RNTI),a Transmit Power Control-SRS RNTI (TPC-SRS-RNTI), an Interruption RNTI(INT-RNTI), a Slot Format Indication RNTI (SFI-RNTI), a Semi-PersistentCSI RNTI (SP-CSI-RNTI), a Modulation and Coding Scheme Cell RNTI(MCS-C-RNTI), and/or the like.

Depending on the purpose and/or content of a DCI, the base station maytransmit the DCIs with one or more DCI formats. For example, DCI format0_0 may be used for scheduling of PUSCH in a cell. DCI format 0_0 may bea fallback DCI format (e.g., with compact DCI payloads). DCI format 0_1may be used for scheduling of PUSCH in a cell (e.g., with more DCIpayloads than DCI format 0_0). DCI format 1_0 may be used for schedulingof PDSCH in a cell. DCI format 1_0 may be a fallback DCI format (e.g.,with compact DCI payloads). DCI format 1_1 may be used for scheduling ofPDSCH in a cell (e.g., with more DCI payloads than DCI format 1_0). DCIformat 2_0 may be used for providing a slot format indication to a groupof UEs. DCI format 2_1 may be used for notifying a group of UEs of aphysical resource block and/or OFDM symbol where the UE may assume notransmission is intended to the UE. DCI format 2_2 may be used fortransmission of a transmit power control (TPC) command for PUCCH orPUSCH. DCI format 2_3 may be used for transmission of a group of TPCcommands for SRS transmissions by one or more UEs. DCI format(s) for newfunctions may be defined in future releases. DCI formats may havedifferent DCI sizes, or may share the same DCI size.

After scrambling a DCI with a RNTI, the base station may process the DCIwith channel coding (e.g., polar coding), rate matching, scramblingand/or QPSK modulation. A base station may map the coded and modulatedDCI on resource elements used and/or configured for a PDCCH. Based on apayload size of the DCI and/or a coverage of the base station, the basestation may transmit the DCI via a PDCCH occupying a number ofcontiguous control channel elements (CCEs). The number of the contiguousCCEs (referred to as aggregation level) may be 1, 2, 4, 8, 16, and/orany other suitable number. A CCE may comprise a number (e.g., 6) ofresource-element groups (REGs). A REG may comprise a resource block inan OFDM symbol. The mapping of the coded and modulated DCI on theresource elements may be based on mapping of CCEs and REGs (e.g.,CCE-to-REG mapping).

FIG. 14A illustrates an example of CORESET configurations for abandwidth part. The base station may transmit a DCI via a PDCCH on oneor more control resource sets (CORESETs). A CORESET may comprise atime-frequency resource in which the UE tries to decode a DCI using oneor more search spaces. The base station may configure a CORESET in thetime-frequency domain. In the example of FIG. 14A, a first CORESET 1401and a second CORESET 1402 occur at the first symbol in a slot. The firstCORESET 1401 overlaps with the second CORESET 1402 in the frequencydomain. A third CORESET 1403 occurs at a third symbol in the slot. Afourth CORESET 1404 occurs at the seventh symbol in the slot. CORESETsmay have a different number of resource blocks in frequency domain.

FIG. 14B illustrates an example of a CCE-to-REG mapping for DCItransmission on a CORESET and PDCCH processing. The CCE-to-REG mappingmay be an interleaved mapping (e.g., for the purpose of providingfrequency diversity) or a non-interleaved mapping (e.g., for thepurposes of facilitating interference coordination and/orfrequency-selective transmission of control channels). The base stationmay perform different or same CCE-to-REG mapping on different CORESETs.A CORESET may be associated with a CCE-to-REG mapping by RRCconfiguration. A CORESET may be configured with an antenna port quasico-location (QCL) parameter. The antenna port QCL parameter may indicateQCL information of a demodulation reference signal (DMRS) for PDCCHreception in the CORESET.

The base station may transmit, to the UE, RRC messages comprisingconfiguration parameters of one or more CORESETs and one or more searchspace sets. The configuration parameters may indicate an associationbetween a search space set and a CORESET. A search space set maycomprise a set of PDCCH candidates formed by CCEs at a given aggregationlevel. The configuration parameters may indicate: a number of PDCCHcandidates to be monitored per aggregation level; a PDCCH monitoringperiodicity and a PDCCH monitoring pattern; one or more DCI formats tobe monitored by the UE; and/or whether a search space set is a commonsearch space set or a UE-specific search space set. A set of CCEs in thecommon search space set may be predefined and known to the UE. A set ofCCEs in the UE-specific search space set may be configured based on theUE's identity

As shown in FIG. 14B, the UE may determine a time-frequency resource fora CORESET based on RRC messages. The UE may determine a CCE-to-REGmapping (e.g., interleaved or non-interleaved, and/or mappingparameters) for the CORESET based on configuration parameters of theCORESET. The UE may determine a number (e.g., at most 10) of searchspace sets configured on the CORESET based on the RRC messages. The UEmay monitor a set of PDCCH candidates according to configurationparameters of a search space set. The UE may monitor a set of PDCCHcandidates in one or more CORESETs for detecting one or more DCIs.Monitoring may comprise decoding one or more PDCCH candidates of the setof the PDCCH candidates according to the monitored DCI formats.Monitoring may comprise decoding a DCI content of one or more PDCCHcandidates with possible (or configured) PDCCH locations, possible (orconfigured) PDCCH formats (e.g., number of CCEs, number of PDCCHcandidates in common search spaces, and/or number of PDCCH candidates inthe UE-specific search spaces) and possible (or configured) DCI formats.The decoding may be referred to as blind decoding. The UE may determinea DCI as valid for the UE, in response to CRC checking (e.g., scrambledbits for CRC parity bits of the DCI matching a RNTI value). The UE mayprocess information contained in the DCI (e.g., a scheduling assignment,an uplink grant, power control, a slot format indication, a downlinkpreemption, and/or the like).

The UE may transmit uplink control signaling (e.g., uplink controlinformation (UCI)) to a base station. The uplink control signaling maycomprise hybrid automatic repeat request (HARQ) acknowledgements forreceived DL-SCH transport blocks. The UE may transmit the HARQacknowledgements after receiving a DL-SCH transport block. Uplinkcontrol signaling may comprise channel state information (CSI)indicating channel quality of a physical downlink channel. The UE maytransmit the CSI to the base station. The base station, based on thereceived CSI, may determine transmission format parameters (e.g.,comprising multi-antenna and beamforming schemes) for a downlinktransmission. Uplink control signaling may comprise scheduling requests(SR). The UE may transmit an SR indicating that uplink data is availablefor transmission to the base station. The UE may transmit a UCI (e.g.,HARQ acknowledgements (HARQ-ACK), CSI report, SR, and the like) via aphysical uplink control channel (PUCCH) or a physical uplink sharedchannel (PUSCH). The UE may transmit the uplink control signaling via aPUCCH using one of several PUCCH formats.

There may be five PUCCH formats and the UE may determine a PUCCH formatbased on a size of the UCI (e.g., a number of uplink symbols of UCItransmission and a number of UCI bits). PUCCH format 0 may have a lengthof one or two OFDM symbols and may include two or fewer bits. The UE maytransmit UCI in a PUCCH resource using PUCCH format 0 if thetransmission is over one or two symbols and the number of HARQ-ACKinformation bits with positive or negative SR (HARQ-ACK/SR bits) is oneor two. PUCCH format 1 may occupy a number between four and fourteenOFDM symbols and may include two or fewer bits. The UE may use PUCCHformat 1 if the transmission is four or more symbols and the number ofHARQ-ACK/SR bits is one or two. PUCCH format 2 may occupy one or twoOFDM symbols and may include more than two bits. The UE may use PUCCHformat 2 if the transmission is over one or two symbols and the numberof UCI bits is two or more. PUCCH format 3 may occupy a number betweenfour and fourteen OFDM symbols and may include more than two bits. TheUE may use PUCCH format 3 if the transmission is four or more symbols,the number of UCI bits is two or more and PUCCH resource does notinclude an orthogonal cover code. PUCCH format 4 may occupy a numberbetween four and fourteen OFDM symbols and may include more than twobits. The UE may use PUCCH format 4 if the transmission is four or moresymbols, the number of UCI bits is two or more and the PUCCH resourceincludes an orthogonal cover code.

The base station may transmit configuration parameters to the UE for aplurality of PUCCH resource sets using, for example, an RRC message. Theplurality of PUCCH resource sets (e.g., up to four sets) may beconfigured on an uplink BWP of a cell. A PUCCH resource set may beconfigured with a PUCCH resource set index, a plurality of PUCCHresources with a PUCCH resource being identified by a PUCCH resourceidentifier (e.g., pucch-Resourceid), and/or a number (e.g. a maximumnumber) of UCI information bits the UE may transmit using one of theplurality of PUCCH resources in the PUCCH resource set. When configuredwith a plurality of PUCCH resource sets, the UE may select one of theplurality of PUCCH resource sets based on a total bit length of the UCIinformation bits (e.g., HARQ-ACK, SR, and/or CSI). If the total bitlength of UCI information bits is two or fewer, the UE may select afirst PUCCH resource set having a PUCCH resource set index equal to “0”.If the total bit length of UCI information bits is greater than two andless than or equal to a first configured value, the UE may select asecond PUCCH resource set having a PUCCH resource set index equal to“1”. If the total bit length of UCI information bits is greater than thefirst configured value and less than or equal to a second configuredvalue, the UE may select a third PUCCH resource set having a PUCCHresource set index equal to “2”. If the total bit length of UCIinformation bits is greater than the second configured value and lessthan or equal to a third value (e.g., 1406), the UE may select a fourthPUCCH resource set having a PUCCH resource set index equal to “3”.

After determining a PUCCH resource set from a plurality of PUCCHresource sets, the UE may determine a PUCCH resource from the PUCCHresource set for UCI (HARQ-ACK, CSI, and/or SR) transmission. The UE maydetermine the PUCCH resource based on a PUCCH resource indicator in aDCI (e.g., with a DCI format 1_0 or DCI for 1_1) received on a PDCCH. Athree-bit PUCCH resource indicator in the DCI may indicate one of eightPUCCH resources in the PUCCH resource set. Based on the PUCCH resourceindicator, the UE may transmit the UCI (HARQ-ACK, CSI and/or SR) using aPUCCH resource indicated by the PUCCH resource indicator in the DCI.

FIG. 15 illustrates an example of a wireless device 1502 incommunication with a base station 1504 in accordance with embodiments ofthe present disclosure. The wireless device 1502 and base station 1504may be part of a mobile communication network, such as the mobilecommunication network 100 illustrated in FIG. 1A, the mobilecommunication network 150 illustrated in FIG. 1B, or any othercommunication network. Only one wireless device 1502 and one basestation 1504 are illustrated in FIG. 15 , but it will be understood thata mobile communication network may include more than one UE and/or morethan one base station, with the same or similar configuration as thoseshown in FIG. 15 .

The base station 1504 may connect the wireless device 1502 to a corenetwork (not shown) through radio communications over the air interface(or radio interface) 1506. The communication direction from the basestation 1504 to the wireless device 1502 over the air interface 1506 isknown as the downlink, and the communication direction from the wirelessdevice 1502 to the base station 1504 over the air interface is known asthe uplink. Downlink transmissions may be separated from uplinktransmissions using FDD, TDD, and/or some combination of the twoduplexing techniques.

In the downlink, data to be sent to the wireless device 1502 from thebase station 1504 may be provided to the processing system 1508 of thebase station 1504. The data may be provided to the processing system1508 by, for example, a core network. In the uplink, data to be sent tothe base station 1504 from the wireless device 1502 may be provided tothe processing system 1518 of the wireless device 1502. The processingsystem 1508 and the processing system 1518 may implement layer 3 andlayer 2 OSI functionality to process the data for transmission. Layer 2may include an SDAP layer, a PDCP layer, an RLC layer, and a MAC layer,for example, with respect to FIG. 2A, FIG. 2B, FIG. 3 , and FIG. 4A.Layer 3 may include an RRC layer as with respect to FIG. 2B.

After being processed by processing system 1508, the data to be sent tothe wireless device 1502 may be provided to a transmission processingsystem 1510 of base station 1504. Similarly, after being processed bythe processing system 1518, the data to be sent to base station 1504 maybe provided to a transmission processing system 1520 of the wirelessdevice 1502. The transmission processing system 1510 and thetransmission processing system 1520 may implement layer 1 OSIfunctionality. Layer 1 may include a PHY layer with respect to FIG. 2A,FIG. 2B, FIG. 3 , and FIG. 4A. For transmit processing, the PHY layermay perform, for example, forward error correction coding of transportchannels, interleaving, rate matching, mapping of transport channels tophysical channels, modulation of physical channel, multiple-inputmultiple-output (MIMO) or multi-antenna processing, and/or the like.

At the base station 1504, a reception processing system 1512 may receivethe uplink transmission from the wireless device 1502. At the wirelessdevice 1502, a reception processing system 1522 may receive the downlinktransmission from base station 1504. The reception processing system1512 and the reception processing system 1522 may implement layer 1 OSIfunctionality. Layer 1 may include a PHY layer with respect to FIG. 2A,FIG. 2B, FIG. 3 , and FIG. 4A. For receive processing, the PHY layer mayperform, for example, error detection, forward error correctiondecoding, deinterleaving, demapping of transport channels to physicalchannels, demodulation of physical channels, MIMO or multi-antennaprocessing, and/or the like.

As shown in FIG. 15 , a wireless device 1502 and the base station 1504may include multiple antennas. The multiple antennas may be used toperform one or more MIMO or multi-antenna techniques, such as spatialmultiplexing (e.g., single-user MIMO or multi-user MIMO),transmit/receive diversity, and/or beamforming. In other examples, thewireless device 1502 and/or the base station 1504 may have a singleantenna.

The processing system 1508 and the processing system 1518 may beassociated with a memory 1514 and a memory 1524, respectively. Memory1514 and memory 1524 (e.g., one or more non-transitory computer readablemediums) may store computer program instructions or code that may beexecuted by the processing system 1508 and/or the processing system 1518to carry out one or more of the functionalities discussed in the presentapplication. Although not shown in FIG. 15 , the transmission processingsystem 1510, the transmission processing system 1520, the receptionprocessing system 1512, and/or the reception processing system 1522 maybe coupled to a memory (e.g., one or more non-transitory computerreadable mediums) storing computer program instructions or code that maybe executed to carry out one or more of their respectivefunctionalities.

The processing system 1508 and/or the processing system 1518 maycomprise one or more controllers and/or one or more processors. The oneor more controllers and/or one or more processors may comprise, forexample, a general-purpose processor, a digital signal processor (DSP),a microcontroller, an application specific integrated circuit (ASIC), afield programmable gate array (FPGA) and/or other programmable logicdevice, discrete gate and/or transistor logic, discrete hardwarecomponents, an on-board unit, or any combination thereof. The processingsystem 1508 and/or the processing system 1518 may perform at least oneof signal coding/processing, data processing, power control,input/output processing, and/or any other functionality that may enablethe wireless device 1502 and the base station 1504 to operate in awireless environment.

The processing system 1508 and/or the processing system 1518 may beconnected to one or more peripherals 1516 and one or more peripherals1526, respectively. The one or more peripherals 1516 and the one or moreperipherals 1526 may include software and/or hardware that providefeatures and/or functionalities, for example, a speaker, a microphone, akeypad, a display, a touchpad, a power source, a satellite transceiver,a universal serial bus (USB) port, a hands-free headset, a frequencymodulated (FM) radio unit, a media player, an Internet browser, anelectronic control unit (e.g., for a motor vehicle), and/or one or moresensors (e.g., an accelerometer, a gyroscope, a temperature sensor, aradar sensor, a lidar sensor, an ultrasonic sensor, a light sensor, acamera, and/or the like). The processing system 1508 and/or theprocessing system 1518 may receive user input data from and/or provideuser output data to the one or more peripherals 1516 and/or the one ormore peripherals 1526. The processing system 1518 in the wireless device1502 may receive power from a power source and/or may be configured todistribute the power to the other components in the wireless device1502. The power source may comprise one or more sources of power, forexample, a battery, a solar cell, a fuel cell, or any combinationthereof. The processing system 1508 and/or the processing system 1518may be connected to a GPS chipset 1517 and a GPS chipset 1527,respectively. The GPS chipset 1517 and the GPS chipset 1527 may beconfigured to provide geographic location information of the wirelessdevice 1502 and the base station 1504, respectively.

FIG. 16A illustrates an example structure for uplink transmission. Abaseband signal representing a physical uplink shared channel mayperform one or more functions. The one or more functions may comprise atleast one of: scrambling; modulation of scrambled bits to generatecomplex-valued symbols; mapping of the complex-valued modulation symbolsonto one or several transmission layers; transform precoding to generatecomplex-valued symbols; precoding of the complex-valued symbols; mappingof precoded complex-valued symbols to resource elements; generation ofcomplex-valued time-domain Single Carrier-Frequency Division MultipleAccess (SC-FDMA) or CP-OFDM signal for an antenna port; and/or the like.In an example, when transform precoding is enabled, a SC-FDMA signal foruplink transmission may be generated. In an example, when transformprecoding is not enabled, an CP-OFDM signal for uplink transmission maybe generated by FIG. 16A. These functions are illustrated as examplesand it is anticipated that other mechanisms may be implemented invarious embodiments.

FIG. 16B illustrates an example structure for modulation andup-conversion of a baseband signal to a carrier frequency. The basebandsignal may be a complex-valued SC-FDMA or CP-OFDM baseband signal for anantenna port and/or a complex-valued Physical Random Access Channel(PRACH) baseband signal. Filtering may be employed prior totransmission.

FIG. 16C illustrates an example structure for downlink transmissions. Abaseband signal representing a physical downlink channel may perform oneor more functions. The one or more functions may comprise: scrambling ofcoded bits in a codeword to be transmitted on a physical channel;modulation of scrambled bits to generate complex-valued modulationsymbols; mapping of the complex-valued modulation symbols onto one orseveral transmission layers; precoding of the complex-valued modulationsymbols on a layer for transmission on the antenna ports; mapping ofcomplex-valued modulation symbols for an antenna port to resourceelements; generation of complex-valued time-domain OFDM signal for anantenna port; and/or the like. These functions are illustrated asexamples and it is anticipated that other mechanisms may be implementedin various embodiments.

FIG. 16D illustrates another example structure for modulation andup-conversion of a baseband signal to a carrier frequency. The basebandsignal may be a complex-valued OFDM baseband signal for an antenna port.Filtering may be employed prior to transmission.

A wireless device may receive from a base station one or more messages(e.g. RRC messages) comprising configuration parameters of a pluralityof cells (e.g. primary cell, secondary cell). The wireless device maycommunicate with at least one base station (e.g. two or more basestations in dual-connectivity) via the plurality of cells. The one ormore messages (e.g. as a part of the configuration parameters) maycomprise parameters of physical, MAC, RLC, PCDP, SDAP, RRC layers forconfiguring the wireless device. For example, the configurationparameters may comprise parameters for configuring physical and MAClayer channels, bearers, etc. For example, the configuration parametersmay comprise parameters indicating values of timers for physical, MAC,RLC, PCDP, SDAP, RRC layers, and/or communication channels.

A timer may begin running once it is started and continue running untilit is stopped or until it expires. A timer may be started if it is notrunning or restarted if it is running. A timer may be associated with avalue (e.g. the timer may be started or restarted from a value or may bestarted from zero and expire once it reaches the value). The duration ofa timer may not be updated until the timer is stopped or expires (e.g.,due to BWP switching). A timer may be used to measure a timeperiod/window for a process. When the specification refers to animplementation and procedure related to one or more timers, it will beunderstood that there are multiple ways to implement the one or moretimers. For example, it will be understood that one or more of themultiple ways to implement a timer may be used to measure a timeperiod/window for the procedure. For example, a random access responsewindow timer may be used for measuring a window of time for receiving arandom access response. In an example, instead of starting and expiry ofa random access response window timer, the time difference between twotime stamps may be used. When a timer is restarted, a process formeasurement of time window may be restarted. Other exampleimplementations may be provided to restart a measurement of a timewindow.

A UE-RRC layer may initiate an RRC connection establishment procedure,an RRC connection resume procedure, or an RRC connectionre-establishment procedure. Based on initiating the RRC connectionestablishment procedure or the RRC connection resume procedure, the UEmay perform one or more procedures:

-   performing a unified access control procedure for access attempt on    a serving cell;-   applying default configurations parameters and    configurations/parameters provided by SIB1, for example, based on    the access attempt being allowed, applying default configurations    and configurations/parameters provided by SIB1;-   starting a timer to supervise those RRC procedures;-   performing sending a random access preamble to the serving cell, for    example, based on the access attempt being allowed;-   sending an RRC request message to the serving cell, for example,    based on determining a reception of a random access response being    successful, sending an RRC request message to the serving cell;-   receiving an RRC response message or an RRC reject message from the    serving cell; or-   sending an RRC complete message, for example, based on receiving the    RRC response message, sending an RRC complete message.-   For the RRC connection re-establishment procedure, the UE may not    perform the unified access procedure.

For initiating those RRC procedures, the UE-RRC layer may use parametersin a received SIB1. The UE-RRC layer may use L1 parameter values and atime alignment timer in the SIB1. The UE-RRC layer may use UAC barringinformation in the SIB1 to perform the unified access control procedure.Based on the unified access control procedure, the UE-RRC layer maydetermine whether the access attempt of those RRC procedures is barredor allowed. Based on the determining the access attempt is allowed, theUE-RRC layer may determine send an RRC request message to a base stationwhere the RRC request message may be an RRC setup request message, anRRC resume request message, or an RRC re-establishment procedure. TheUE-NAS layer may or may not provide S-TMSI as an UE identity. The UE-RRClayer may set an UE identity in the RRC request message.

For the RRC setup request message, the UE-RRC layer may set the UEidentity to S-TMSI if the UE-NAS layer provides the S-TMSI. Otherwise,the UE-RRC layer may draw a 39-bit random value and set the UE identityto the random value. For the RRC resume request message, the UE-RRClayer may set the UE identity to resume identity stored. For the RRCreestablishment request message, the UE-RRC layer may set the UEidentity to C-RNTI used in the source PCell. The UE-NAS layer mayprovide an establishment cause (e.g., UE-NAS layer). The UE-RRC layermay set the establishment cause for the RRC request message.

For the RRC resume request message, the UE-RRC layer may restoreparameters and security keys/parameters from the stored UE inactive AScontext. Based on the security keys/parameters, the UE-RRC layer may seta resume MAC-I value to the 16 least significant bits of the MAC-Icalculated based on variable resume MAC input, security key of integrityprotection for RRC layer in a UE inactive AS context, the previousconfigured integrity protection algorithm, and other security parameters(e.g., count, bearer and direction). The variable resume MAC input maycomprise physical cell identity and C-RNTI of a source cell, and cellidentity of a target cell. The UE-RRC layer may include the resume MAC-Iin the RRC resume request message. Based on the securitykeys/parameters, the UE-RRC layer derive new security keys for integrityprotection and ciphering, and configure lower layers (e.g. MAC layer) toapply them. The UE-RRC layer may re-establish PDCP entities for SRB1 andresume SRB1.

For the RRC reestablishment request message, the UE-RRC layer maycontain the physical cell identity of the source PCell and a short MAC-Iin the RRC reestablishment message. The UE-RRC layer may set the shortMAC-I to the 16 east significant bits of the MAC-I calculated based onvariable short MAC input, security key of integrity protection for RRClayer and the integrity protection algorithm, which was used in a sourcePCell or the PCell in which the trigger for the reestablishmentoccurred, and other security parameters (e.g., count, bearer anddirection). The variable short MAC input may comprise physical cellidentity and C-RNTI of a source cell, and cell identity of a targetcell. The UE-RRC layer may re-establish PDCP entities and RLC entitiesfor SRB1 and apply a default SRB1 configuration parameters for SRB1. TheUE-RRC layer may configure lower layers (e.g. PDCP layer) to suspendintegrity protection and ciphering for SRB1 and resume SRB1.

A UE-RRC layer may send an RRC request message to lower layers (e.g.,PDCP layer, RLC layer, MAC layer and/or PHY layer) for transmission.

A UE-RRC layer may receive an RRC setup message in response to an RRCresume request message or an RRC reestablishment request message. Basedon the RRC setup message, the UE-RRC layer may discard any sorted AScontext, suspend configuration parameters and any current AS securitycontext. The UE-RRC layer may release radio resources for allestablished RBs except SRB0, including release of the RLC entities, ofthe associated PDCP entities and of SDAP. The UE-RRC layer may releasethe RRC configuration except for default L1 parameter values, defaultMAC cell group configuration and CCCH configuration. The UE-RRC layermay indicate to upper layers (e.g., NAS layer) fallback of the RRCconnection. The UE-RRC layer may stop timer T380 if running where thetimer T380 is periodic RNA update timer.

A UE-RRC layer may receive an RRC setup message in response to an RRCsetup request message, an RRC resume request message or an RRCreestablishment request message. Based on configurations parameters inthe received RRC setup message. Based on the RRC setup message, theUE-RRC layer may perform a cell group configuration or radio bearerconfiguration. The UE-RRC layer may stop a barring timer and wait timerfor the cell sending the RRC setup message. Based on receiving the RRCsetup message, the UE-RRC layer may perform one or more of thefollowing:

-   enter RRC connected state;-   stop a cell re-selection procedure;-   consider the current cell sending the RRC setup message to be the    PCell; or/and-   send an RRC setup complete message by setting the content of the RRC    setup complete message.

A UE-RRC layer may receive an RRC resume message in response to an RRCresume request message. Based on the RRC resume message, the UE-RRClayer may discard a UE inactive AS context and release a suspendconfiguration parameters except ran notification area information. Basedon configuration parameters in the RRC resume message, the UE-RRC layermay perform a cell group configuration, a radio bearer configuration,security key update procedure, measurement configuration procedure.Based on receiving the RRC resume message, the UE-RRC layer may performone or more of the following:

-   indicate upper layers (e.g., NAS layer) that the suspended RRC    connection has been resumed;-   resume SRB2, all DRBs and measurements;-   enter RRC connected state;-   stop a cell re-selection procedure;-   consider the current cell sending the RRC resume message to be the    PCell; or/and-   send an RRC resume complete message by setting the content of the    RRC resume complete message.

A UE-RRC layer may receive an RRC reject message in response to an RRCsetup request message or an RRC resume request message. The RRC rejectmessage may contain wait timer. Based on the wait timer, the UE-RRClayer may start timer T302, with the timer value set to the wait timer.Based on the RRC reject message, the UE-RRC layer may inform upperlayers (e.g., UE-NAS layer) about the failure to setup an RRC connectionor resume an RRC connection. The UE-RRC layer may reset MAC and releasethe default MAC Cell Group configuration. Based on the RRC Rejectreceived in response to a request from upper layers, the UE-RRC layermay inform the upper layer (e.g., NAS layer) that access barring isapplicable for all access categories except categories ‘0’ and ‘2’.

A UE-RRC layer may receive an RRC reject message in response to an RRCresume request message. Based on the RRC reject message, The UE-RRClayer may discard current security keys. The UE-RRC layer may suspendSRB1. The UE-RRC layer may set pending rna update value to true ifresume is triggered due to an RNA update.

A UE-RRC layer may perform a cell (re)selection procedure whileperforming a RRC procedure to establish an RRC connection. Based on cellselection or cell reselection, the UE-RRC layer may change a cell on theUE camped and stop the RRC procedure. The UE-RRC layer may inform upperlayers (e.g., NAS layer) about the failure of the RRC procedure.

A UE may fail in a random access procedure to establish connection witha base station. A UE may store connection establishment failureinformation. The connection establishment failure information maycomprise at least one of: a failed cell identity which is the globalcell identity of a cell where connection establishment failure isdetected; location information of the UE comprising coordinates of thelocation and/or the horizontal velocity of the UE; measurement resultsof the failed cell comprising RSRP and RSRQ, if available, of the cellwhere connection establishment failure is detected and based onmeasurements collected up to the moment the UE detected the failure;measurements of neighbour cells; time since failure indicating the timethat elapsed since the last connection establishment failure; a numberof preambles sent indicating the number of preambles sent by MAC for thefailed random access procedure; contention detected indicating whethercontention resolution was not successful for at least one of thetransmitted preambles for the failed random access procedure; or maximumtransmission power reached indicating whether or not the maximum powerlevel was used for the last transmitted preamble. The UE may send areport comprising the connection establishment failure information(e.g., a connection establishment failure report) to a base station.

A UE may fail in a RACH procedure. The UE may store the RACH failureinformation. The RACH failure information may comprise at least one of anumber of preambles sent indicating the number of preambles sent by MACfor the failed random access procedure or contention detected indicatingwhether contention resolution was not successful for at least one of thetransmitted preambles for the failed random access procedure. The UE maysend a report comprising the rach failure information (e.g., a rachreport) to a base station.

Based on receiving an RRC reconfiguration message from a base station, aUE-RRC layer may perform reconfiguration with sync in at least one ofthe following cases: (1) reconfiguration with sync and security keyrefresh, involving random access (RA) to the PCell/PSCell, MAC reset,refresh of security and re-establishment of RLC and PDCP triggered byexplicit layer 2 (L2) indicators; or (2) reconfiguration with sync butwithout security key refresh, involving RA to the PCell/PSCell, MACreset and RLC re-establishment and PDCP data recovery (for AM DRB)triggered by explicit L2 indicators.

A UE-RRC layer may receive an RRC reconfiguration message withreconfiguration sync information element (IE) or mobility controlinformation from a base station. Based on the RRC reconfigurationmessage, the UE may perform a random access procedure to a base stationindicated in the reconfiguration sync IE or mobility control informationin the RRC reconfiguration message. Based on the random access procedurebeing successfully completed, the UE may send an RRC reconfigurationcomplete message to the base station. The UE and the base station mayconsider sending/receiving the RRC reconfiguration complete messagesuccessfully as reconfiguration with sync completion. Thereconfiguration with sync completion may include at least one ofhandover completion or PSCell addition for cell group addition.

For normal service, a UE may camp on a suitable cell, monitor controlchannel(s) of the camped on cell. From the camped on cell, the UE mayreceive system information (SI) from the PLMN. The UE may receiveregistration area information from the PLMN (e.g., tacking area code(TAC)) and receive other AS and NAS Information from the SI. The UE mayreceive paging and notification messages from the PLMN and initiatetransfer to connected mode if the UE is registered in the PLMN. The UEmay regularly search for a better cell according to the cell reselectioncriteria. If a better cell is found, that cell is selected. The UE maycamped on the selected cell.

A base station may provide priorities of different frequencies on sameRAT or inter-RAT frequencies to a UE in system information, in dedicatedsignaling (e.g., an RRC release message), or by inheriting from anotherRAT at inter RAT cell (re)selection. The UE may store the priorities offrequencies provided by the dedicated signaling.

A base station may provide redirection information. The redirectioninformation may comprise at least one of one or more frequencies or oneor more core network types. An RRC release message comprise theredirection information. The base station may provide the RRC releasemessage to transition a UE to RRC inactive or RRC inactive state. Basedon the RRC release message, the UE may perform cell selection procedure.Based on the redirection information, the UE may perform a cellselection procedure to find a suitable cell if the RRC release messagecontains the redirection information. Otherwise, the UE may perform thecell selection procedure on a carrier of RAT which the UE selectscurrently (e.g., NR carrier or LTE carrier).

A UE in RRC idle or RRC inactive state may perform one of two proceduressuch as initial cell selection and cell selection by leveraging storedinformation. The UE may perform the initial cell selection when the UEdoesn't have stored cell information for the selected PLMN. Otherwise,the UE may perform the cell selection by leveraging stored information.For initial cell selection, a UE may scan all RF channels in the NRbands according to its capabilities to find a suitable cell. Based onresults of the scan, the UE may search for the strongest cell on eachfrequency. The UE may select a cell which is a suitable cell. For thecell selection by leveraging stored information, the UE may requiresstored information of frequencies and optionally also information oncell parameters from previously received measurement control informationelements or from previously detected cells. Based on the storedinformation, the UE may search a suitable cell and select the suitablecell if the UE found the suitable cell. If the UE does not found thesuitable cell, the UE may perform the initial cell selection.

A base station may configure cell selection criteria for cell selection.a UE may seek to identify a suitable cell for the cell selection. Thesuitable cell is one for which satisfies following conditions: (1) themeasured cell attributes satisfy the cell selection criteria, (2) thecell PLMN is the selected PLMN, registered or an equivalent PLMN, (3)the cell is not barred or reserved, and (4) the cell is not part oftracking area which is in the list of “forbidden tracking areas forroaming”. An RRC layer in a UE may inform a NAS layer in the UE of cellselection and reselection result based on changes in received systeminformation relevant for NAS. For example, the cell selection andreselection result may be a cell identity, tracking area code and a PLMNidentity.

A UE may detect a failure of a connection with a base station. Thefailure comprises at least one of:

-   a radio link failure;-   a reconfiguration with sync failure;-   a mobility failure from new radio (NR);-   an integrity check failure indication from lower layers (e.g., PDCP    layer) concerning signaling radio bearer 1 (SRB1) or signaling radio    bearer 2 (SRB2); or-   an RRC connection reconfiguration failure.-   The radio link failure may be a radio link failure of a primary cell    of the base station. The base station may send a reconfiguration    with sync in an RRC message to the UE in RRC connected state. The    reconfiguration with sync may comprise a reconfiguration timer    (e.g., T304). Based on receiving the reconfiguration sync, the UE    may start the reconfiguration timer and perform the reconfiguration    with sync (e.g., handover). Based on expiry of the reconfiguration    timer, the UE determine the reconfiguration sync failure. A base    station may send mobility from NR command message to the UE in RRC    connected state. Based on receiving the mobility from NR command    message, the UE may perform to handover from NR to a cell using    other RAT (e.g., E-UTRA). The UE may determine the mobility failure    from NR based on at least one of conditions being met:-   if the UE does not succeed in establishing the connection to the    target radio access technology; or-   if the UE is unable to comply with any part of the configuration    included in the mobility from NR command message; or-   if there is a protocol error in the inter RAT information included    in the mobility from NR message.

Based on detecting the failure, the UE may initiate an RRC connectionreestablishment procedure. Based on initiating the RRC connectionreestablishment procedure, the UE may start a timer T311, suspend allradio bearers except for SRB0, reset MAC (layer). Based on initiatingthe RRC connection reestablishment procedure, the UE may release MCGSCells, release special cell (SpCell) configuration parameters andmulti-radio dual connectivity (MR-DC) related configuration parameters.For example, based on initiating the RRC connection reestablishmentprocedure, the UE may release master cell group configurationparameters.

Cell group configuration parameters may be used to configure a mastercell group (MCG) or secondary cell group (SCG). If the cell groupconfiguration parameters are used to configure the MCG, the cell groupconfiguration parameters are master cell group configuration parameters.If the cell group configuration parameters are used to configure theSCG, the cell group configuration parameters are secondary cell groupconfiguration parameters. A cell group comprises of one MAC entity, aset of logical channels with associated RLC entities and of a primarycell (SpCell) and one or more secondary cells (SCells). The cell groupconfiguration parameters (e.g., master cell group configurationparameters or secondary cell group configuration parameters) maycomprise at least one of RLC bearer configuration parameters for thecell group, MAC cell group configuration parameters for the cell group,physical cell group configuration parameters for the cell group, SpCellconfiguration parameters for the cell group or SCell configurationparameters for the cell group. The MAC cell group configurationparameters may comprise MAC parameters for a cell group wherein the MACparameters may comprise at least DRX parameters. The physical cell groupconfiguration parameters may comprise cell group specific L1 (layer 1)parameters.

The special cell (SpCell) may comprise a primary cell (PCell) of an MCGor a primary SCG cell (PSCell) of a SCG. The SpCell configurationparameters may comprise serving cell specific MAC and PHY parameters fora SpCell. The MR-DC configuration parameters may comprise at least oneof SRB3 configuration parameters, measurement configuration parameterfor SCG, SCG configuration parameters.

Based on initiating the RRC connection reestablishment procedure, the UEmay perform a cell selection procedure. Based on the cell selectionprocedure, the UE may select a cell based on a signal quality of thecell exceeding a threshold. The UE may select a cell based on a signalquality of the cell exceeding a threshold. The UE may determine, basedon a cell selection procedure, the selected cell exceeding thethreshold. The signal quality comprises at least one of:

-   a reference signal received power;-   a received signal strength indicator;-   a reference signal received quality; or-   a signal to interference plus noise ratio.

Based on selecting a suitable cell, the UE may stop the timer 311 andstart a timer T301. Based on selecting the suitable cell, the UE maystop a barring timer T390 for all access categories. Based on stoppingthe barring timer T390, the UE may consider a barring for all accesscategory to be alleviated for the cell. Based on selecting the cell, theUE may apply the default L1 parameter values except for the parametersprovided in SIB1, apply the default MAC Cell Group configuration, applythe CCCH configuration, apply a timer alignment timer in SIB1 andinitiate transmission of the RRC reestablishment request message.

The UE may stop the timer T301 based on reception of an RRC responsemessage in response of the RRC reestablishment request message. The RRCresponse message may comprise at least one of RRC reestablishmentmessage or RRC setup message or RRC reestablishment reject message. TheUE may stop the timer T301 when the selected cell becomes unsuitable.

Based on the cell selection procedure triggered by initiating the RRCconnection reestablishment procedure, the UE may select an inter-RATcell. Based on selecting an inter-RAT cell, the UE (UE-AS layer) may goto RRC IDLE state and may provide a release cause ‘RRC connectionfailure’ to upper layers (UE-NAS layer) of the UE.

Based on initiating the transmission of the RRC reestablishment requestmessage, the UE may send the RRC reestablishment message. The RRCreestablishment message may comprise at least one of C-RNTI used in thesource PCell, a physical cell identity (PCI) of the source PCell, shortMAC-I or a reestablishment cause. The reestablishment cause may compriseat least one of reconfiguration failure, handover failure or otherfailure.

Based on initiating the transmission of the RRC reestablishment requestmessage, the UE (RRC layer) may re-establish PDCP for SRB1, re-establishRLC for SRB1, apply default SRB configurations for SRB1, configure lowerlayers (PDCP layer) to suspend integrity protection and ciphering forSRB1, resume SRB1 and submit the RRC reestablishment request message tolower layers (PDCP layer) for transmission. Based on submitting the RRCreestablishment request message to lower layers, the UE may send the RRCreestablishment request message to a target base station via the cellselected based on the cell selection procedure wherein the target basestation may or may not be the source base station.

Based on expiry of the timer T311 or T301, the UE (UE-AS layer) may goto RRC IDLE state and may provide a release cause ‘RRC connectionfailure’ to upper layers (UE-NAS layer) of the UE.

Based on receiving the release cause ‘RRC connection failure’, the UE(UE-NAS layer) may perform a NAS signaling connection recovery procedurewhen the UE does not have signaling pending and user data pending. Basedon performing the NAS signaling connection recovery procedure, the UEmay initiate the registration procedure by sending a Registrationrequest message to the AMF.

Based on receiving the release cause ‘RRC connection failure’, the UE(UE-NAS layer) may perform a service request procedure by sending aservice request message to the AMF when the UE has signaling pending oruser data pending.

Based on receiving the RRC reestablishment request message, the targetbase station may check whether the UE context of the UE is locallyavailable. Based on the UE context being not locally available, thetarget base station may perform a retrieve UE context procedure bysending a retrieve UE context request message to the source base station(the last serving base station) of the UE.

For RRC connection reestablishment procedure, the retrieve UE contextrequest message may comprise at least one of a UE context ID, integrityprotection parameters or a new cell identifier. The UE context ID maycomprise at least one of C-RNTI contained the RRC reestablishmentrequest message, a PCI of the source PCell (the last serving PCell). Theintegrity protection parameters for the RRC reestablishment may be theshort MAC-I. The new cell identifier may be an identifier of the targetcell wherein the target cell is a cell where the RRC connection has beenrequested to be re-established.

For the RRC connection reestablishment procedure, based on receiving theretrieve UE context request message, the source base station may checkthe retrieve UE context request message. If the source base station isable to identify the UE context by means of the UE context ID, and tosuccessfully verify the UE by means of the integrity protectioncontained in the retrieve UE context request message, and decides toprovide the UE context to the target base station, the source basestation may respond to the target base station with a retrieve UEcontext response message. If the source base station is not able toidentify the UE context by means of the UE context ID, or if theintegrity protection contained in the retrieve UE context requestmessage is not valid, the source base station may respond to the targetbase station with a retrieve UE context failure message.

For the RRC connection reestablishment procedure, the retrieve UEcontext response message may comprise at least one of Xn applicationprotocol (XnAP) ID of the target base station, XnAP ID of the sourcebase station, globally unique AMF identifier (GUAMI) or UE contextinformation (e.g., UE context information retrieve UE context response).The UE context information may comprise at least one of a NG-C UEassociated signaling reference, UE security capabilities, AS securityinformation, UE aggregate maximum bit rate, PDU session to be setuplist, RRC context, mobility restriction list or index to RAT/frequencyselection priority. The NG-C UE associated signaling reference may be aNG application protocol ID allocated at the AMF of the UE on the NG-Cconnection with the source base station. The AS security information maycomprise a security key of a base station (K_(gNB)) and next hopchaining count (NCC) value. The PDU session to be setup list maycomprise PDU session resource related information used at UE context inthe source base station. The PDU session resource related informationmay comprise a PDU session ID, a PDU session resource aggregate maximumbitrate, a security indication, a PDU session type or QoS flows to besetup list. The security indication may comprise a user plane integrityprotection indication and confidentiality protection indication whichindicates the requirements on user plane (UP) integrity protection andciphering for the corresponding PDU session, respectively. The securityindication may also comprise at least one of an indication whether UPintegrity protection is applied for the PDU session, an indicationwhether UP ciphering is applied for the PDU session and the maximumintegrity protected data rate values (uplink and downlink) per UE forintegrity protected DRBs. The PDU session type may indicate at least oneof internet protocol version 4 (IPv4), IPv6, IPv4v6, ethernet orunstructured. The QoS flow to be setup list may comprise at least one ofQoS flow identifier, QoS flow level QoS parameters (the QoS Parametersto be applied to a QoS flow) or bearer identity.

For the RRC connection reestablishment procedure, the retrieve UEcontext failure message may comprise at least XnAP ID of the target basestation and a cause value.

For the RRC connection reestablishment procedure, based on receiving theretrieve UE context response message, the target base station may sendan RRC reestablishment message to the UE. The RRC reestablishmentmessage may comprise at least a network hop chaining count (NCC) value.

Based on receiving the RRC reestablishment message, the UE may derive anew security key of a base station (K_(gNB)) based on at least one ofcurrent K_(gNB) or next hop (NH) parameters associated to the NCC value.Based on the new security key of the base station and a previouslyconfigured integrity protection algorithm, the UE may derive a securitykey for integrity protection of an RRC signaling (K_(RRCint)) and asecurity key for integrity protection of user plane (UP) data(K_(UPint)). Based on the new security key of the base station and apreviously configured ciphering algorithm, the UE may derive a securitykey for ciphering of an RRC signaling (K_(RRCenc)) and a security keyfor ciphering of user plane (UP) data (K_(UPenc)). Based on theK_(RRCint), and the previously configured integrity protectionalgorithm, the UE may verify the integrity protection of the RRCreestablishment message. Based on the verifying being failed, the UE(UE-AS layer) may go to RRC IDLE state and may provide a release cause‘RRC connection failure’ to upper layers (UE-NAS layer) of the UE. Basedon the verifying being successful, the UE may configure to resumeintegrity protection for SRB1 based on the previously configuredintegrity protection algorithm and the K_(RRCint) and configure toresume ciphering for SRB1 based on the previously configured cipheringalgorithm and K_(RRCenc). The UE may send an RRC reestablishmentcomplete message to the target base station.

Based on receiving the retrieve UE context failure message, the targetbase station may send an RRC release message to the UE. For example,based on the retrieve UE context failure message comprising the RRCrelease message, the target base station may send the RRC releasemessage to the UE. Based on receiving the retrieve UE context failuremessage, the target base station may send an RRC setup message or an RRCreject message. Based on receiving the retrieve UE context failuremessage, the target base station may not send any response message tothe UE.

FIG. 17 illustrates an example of an RRC connection reestablishmentprocedure. The UE in an RRC connected state may send and receive datato/from a first base station (for example, a source base station) via acell 1 wherein the cell 1 is a primary cell of the first base station.The UE may detect a failure of a connection with the first base station.Based on the failure, the UE may initiate the RRC reestablishmentprocedure. Based on initiating the RRC connection reestablishmentprocedure, the UE may start a timer T311, suspend all radio bearersexcept for SRB0, and/or reset a MAC (layer). Based on initiating the RRCconnection reestablishment procedure, the UE may release MCG SCells,release the special cell (SpCell) configuration parameters and themulti-radio dual connectivity (MR-DC) related configuration parameters.Based on initiating the RRC connection reestablishment procedure, the UEmay perform a cell selection procedure. Based on the cell selectionprocedure, the UE may select a cell 2 of a second base station (forexample, a target base station) wherein the cell 2 is a suitable cell.Based on selecting a suitable cell, the UE may stop the timer T311 andstart a timer T301. Based on selecting the suitable cell, the UE maystop a barring timer T390 for all access categories. Based on stoppingthe barring timer T390, the UE may consider a barring for all accesscategory to be alleviated for the cell. Based on selecting the cell, theUE may apply the default L1 parameter values except for the parametersprovided in SIB1, apply the default MAC Cell Group configuration, applythe CCCH configuration, apply a timer alignment timer in SIB1 andinitiate transmission of the RRC reestablishment request message. TheRRC reestablishment message may comprise at least one of C-RNTI used inthe source PCell (e.g., the cell 1), a physical cell identity (PCI) ofthe source PCell, short MAC-I or a reestablishment cause. Based oninitiating the transmission of the RRC reestablishment request message,the UE (RRC layer) may re-establish PDCP for SRB1, re-establish RLC forSRB1, apply default SRB configurations for SRB1, configure lower layers(PDCP layer) to suspend integrity protection and ciphering for SRB1,resume SRB1 and submit the RRC reestablishment request message to lowerlayers (PDCP layer) for transmission. Based on initiating thetransmission of the RRC reestablishment request message, the UE may sendthe RRC reestablishment request message to the second base station viathe cell 2. Based on receiving the RRC reestablishment request message,the second base station may check whether the UE context of the UE islocally available. Based on the UE context being not locally available,the second base station may perform the retrieve UE context procedure bysending a retrieve UE context request message to the source base stationof the UE. The retrieve UE context request message may comprise at leastone of C-RNTI, a PCI of the source PCell (the last serving PCell) orshort MAC-I. Based on receiving the retrieve UE context request message,the source base station may check the retrieve UE context requestmessage. If the source base station is able to identify the UE contextby means of the C-RNTI, and to successfully verify the UE by means ofthe short MAC-I, and decides to provide the UE context to the secondbase station, the source base station may respond to the second basestation with a retrieve UE context response message. The retrieve UEcontext response message may comprise at least of GUAMI or the UEcontext information. Based on receiving the retrieve UE context responsemessage, the second base station may send an RRC reestablishment messageto the UE. The RRC reestablishment message may comprise a network hopchaining count (NCC) value. Based on receiving the RRC reestablishmentmessage, the UE may derive a new security key of a base station(K_(gNB)) based on at least one of current K_(gNB) or next hop (NH)parameters associated to the NCC value. Based on the new security key ofa base station (K_(gNB)) and the previously configured securityalgorithms, the UE may derive security keys for integrity protection andciphering of RRC signaling (e.g., K_(RRCint) and K_(RRCenc)respectively) and user plane (UP) data (e.g., K_(UPint) and K_(UPenc)respectively). Based on the security key for integrity protection of theRRC signaling (K_(RRCint)), the UE may verify the integrity protectionof the RRC reestablishment message. Based on the verifying beingsuccessful, the UE may configure to resume integrity protection for SRB1based on the previously configured integrity protection algorithm andthe K_(RRCint) and configure to resume ciphering for SRB1 based on thepreviously configured ciphering algorithm and the K_(RRCenc). The secondbase station may send a first RRC reconfiguration message. The RRC firstreconfiguration message may comprise the SpCell configurationparameters. Based on receiving the SpCell configuration parameters, theUE may initiate transmission and reception of data to/from the secondbase station. The UE may send an RRC reestablishment complete message tothe second base station. The RRC reestablishment complete message maycomprise measurement report. Based on receiving the measurement report,the second base station may determine to configure SCells and/orsecondary cell groups (e.g., SCG or PSCells). Based on the determining,the second base station may send a second RRC reconfiguration messagecomprising SCells configuration parameters and/or MR-DC relatedconfiguration parameters. Based receiving the second RRC reconfigurationmessage, the UE may transmit and receive data via the SCells and/orSCGs.

The RRC reconfiguration message may comprise at least one of cell groupconfiguration parameters of MCG and/or SCG, radio bearer configurationparameters or AS security key parameters.

A UE may remain in CM-CONNECTED and move within an area configured bythe base station without notifying the base station when the UE is inRRC inactive state where the area is an RNA. In RRC inactive state, alast serving base station may keep the UE context and the UE-associatedNG connection with the serving AMF and UPF. Based on received downlinkdata from the UPF or downlink UE-associated signaling from the AMF whilethe UE is in RRC inactive state, the last serving base station may pagein the cells corresponding to the RNA and may send RAN Paging via an Xninterface to neighbor base station(s) if the RNA includes cells ofneighbor base station(s).

An AMF may provide to the base station a core network assistanceinformation to assist the base station's decision whether a UE can besent to RRC inactive state. The core network assistance information mayinclude the registration area configured for the UE, the periodicregistration update timer, a UE identity index value, the UE specificDRX, an indication if the UE is configured with mobile initiatedconnection only (MICO) mode by the AMF, or the expected UE behavior. Thebase station may use the UE specific DRX and the UE identity index valueto determine a paging occasion for RAN paging. The base station may useperiodic registration update timer to configure periodic RNA updatetimer (e.g., a timer T380). The base station may use an expected UEbehavior to assist the UE RRC state transition decision.

A base station may initiate a RRC connection release procedure totransit an RRC state of a UE from RRC connected state to RRC idle state,from an RRC connected state to RRC inactive state, from RRC inactivestate back to RRC inactive state when the UE tries to resume, or fromRRC inactive state to RRC idle state when the UE tries to resume. TheRRC connection procedure may also be used to release an RRC connectionof the UE and redirect a UE to another frequency. The base station maysend the RRC release message comprising suspend configuration parameterswhen transitioning RRC state of the UE to RRC inactive state. Thesuspend configuration parameters may comprise at least one of a resumeidentity, RNA configuration, RAN paging cycle, or network hop chainingcount (NCC) value wherein the RNA configuration may comprise RNAnotification area information, or periodic RNA update timer value (e.g.,T380 value). The base station may use the resume identity (e.g.,inactive-RNTI (I-RNTI)) to identify the UE context when the UE is in RRCinactive state.

If the base station has a fresh and unused pair of {NCC, next hop (NH)},the base station may include the NCC in the suspend configurationparameters. Otherwise, the base station may include the same NCCassociated with the current K_(gNB) in the suspend configurationparameters. The NCC is used for AS security. The base station may deletethe current AS keys (e.g., K_(RRCenc), K_(UPenc)), and K_(UPint) aftersending the RRC release message comprising the suspend configurationparameters to the UE but may keep the current AS key K_(RRCint). If thesent NCC value is fresh and belongs to an unused pair of {NCC, NH}, thebase station may save the pair of {NCC, NH} in the current UE ASsecurity context and may delete the current AS key K_(gNB). If the sentNCC value is equal to the NCC value associated with the current K_(gNB),the base station may keep the current AS key K_(gNB) and NCC. The basestation may store the sent resume identity together with the current UEcontext including the remainder of the AS security context.

Upon receiving the RRC release message comprising the suspendconfiguration parameters from the base station, the UE may verify thatthe integrity of the received RRC release message comprising the suspendconfiguration parameters is correct by checking PDCP MAC-I. If thisverification is successful, then the UE may take the received NCC valueand save it as stored NCC with the current UE context. The UE may deletethe current AS keys K_(RRCenc), K_(UPenc), and K_(UPint), but keep thecurrent AS key K_(RRCint) key. If the stored NCC value is different fromthe NCC value associated with the current K_(gNB), the UE may delete thecurrent AS key K_(gNB). If the stored NCC is equal to the NCC valueassociated with the current K_(gNB), the UE shall keep the current ASkey KgNB. The UE may store the received resume identity together withthe current UE context including the remainder of the AS securitycontext, for the next state transition.

Based on receiving the RRC release message comprising the suspendconfiguration parameters, the UE may reset MAC, release the default MACCell Group configuration, re-establish RLC entities for SRB1. Based onreceiving the RRC release message comprising suspend configurationparameters, the UE may store in the UE inactive AS context currentconfiguration parameters. The current configuration parameters maycomprise the current K_(gNB) and K_(RRCint) keys, a robust headercompression (ROHC) state, stored QoS flow to DRB mapping rules, theC-RNTI used in the source PCell, the cell identity and the physical cellidentity of the source PCell, and all other parameters configured exceptfor the ones within reconfiguration with sync and serving cellconfiguration common parameters in SIB. The serving cell configurationcommon parameters in SIB may be used to configure cell specificparameters of a UE's serving cell in SIB1. Based on receiving the RRCrelease message comprising the suspend configuration parameters, the UEmay suspend all SRB(s) and DRB(s) except for SRB0. Based on receivingthe RRC release message comprising suspend configuration parameters, theUE may start a timer T380, enter RRC inactive state, perform cellselection procedure.

The UE in RRC inactive state may initiate an RRC connection resumeprocedure. For example, based on having data or signaling to transmit,or receiving RAN paging message, the UE in RRC inactive state mayinitiate the RRC connection resume procedure. Based on initiating theRRC connection resume procedure, the UE may select access category basedon triggering condition of the RRC connection resume procedure andperform unified access control procedure based on the access category.Based on the unified access control procedure, the UE may consideraccess attempt for the RRC connection resume procedure as allowed. Basedon considering the access attempt as allowed, the UE may apply thedefault L1 parameter values as specified in corresponding physical layerspecifications, except for the parameters for which values are providedin SIB1, apply the default SRB1 configuration, apply the CCCHconfiguration, apply the time alignment timer common included in SIB1,apply the default MAC cell group configuration, start a timer T319 andinitiate transmission of an RRC resume request message.

Based on initiating the transmission of the RRC resume request message,the UE may set the contexts of the RRC resume request message. The RRCresume request message may comprise at least one of resume identity,resume MAC-I or resume cause. The resume cause may comprise at least oneof emergency, high priority access, mt access, mo signalling, mo data,mo voice call, mo sms, ran update, mps priority access, mcs priorityaccess.

Based on initiating the transmission of the RRC resume request message,the UE may restore RRC configuration parameters and the K_(gNB) andK_(RRCint) keys from the stored UE inactive AS context except for themaster cell group configuration parameters, MR-DC related configurationparameters (e.g., secondary cell group configuration parameters) andPDCP configuration parameters. The RRC configuration parameter maycomprise at least one of the C-RNTI used in the source PCell, the cellidentity and the physical cell identity of the source PCell, and allother parameters configured except for the ones within reconfigurationwith sync and serving cell configuration common parameters in SIB. Basedon current (restored) K_(gNB) or next hop (NH) parameters associated tothe stored NCC value, the UE may derive a new key of a base station(K_(gNB)). Based on the new key of the base station, the UE may derivesecurity keys for integrity protection and ciphering of RRC signalling(e.g., K_(RRCenc) and K_(RRCint) respectively) and security keys forintegrity protection and ciphering of user plane data (e.g., K_(UPint)and the K_(UPenc) respectively). Based on configured algorithm and theK_(RRCint) and K_(UPint), the UE may configure lower layers (e.g., PDCPlayer) to apply integrity protection for all radio bearers except SRB0.Based on configured algorithm and the K_(RRCenc) and the K^(UPenc), theUE may configure lower layers (e.g., PDCP layer) to apply ciphering forall radio bearers except SRB0.

Based on initiating the transmission of the RRC resume request message,the UE may re-establish PDCP entities for SRB1, resume SRB1 and submitthe RRC resume request message to lower layers wherein the lower layersmay comprise at least one of PDCP layer, RLC layer, MAC layer orphysical (PHY) layer.

A target base station may receive the RRC resume request message. Basedon receiving the RRC resume request message, the target base station maycheck whether the UE context of the UE is locally available. Based onthe UE context being not locally available, the target base station mayperform the retrieve UE context procedure by sending the retrieve UEcontext request message to the source base station (the last servingbase station) of the UE. The retrieve UE context request message maycomprise at least one of a UE context ID, integrity protectionparameters, a new cell identifier or the resume cause wherein the resumecause is in the RRC resume request message.

For the RRC connection resume procedure, based on receiving the retrieveUE context request message, the source base station may check theretrieve UE context request message. If the source base station is ableto identify the UE context by means of the UE context ID, and tosuccessfully verify the UE by means of the integrity protectioncontained in the retrieve UE context request message, and decides toprovide the UE context to the target base station, the source basestation may respond to the target base station with the retrieve UEcontext response message. If the source base station is not able toidentify the UE context by means of the UE context ID, or if theintegrity protection contained in the retrieve UE context requestmessage is not valid, or, if the source base station decides not toprovide the UE context to the target base station, the source basestation may respond to the target base station with a retrieve UEcontext failure message.

For the RRC connection resume procedure, the retrieve UE context failuremessage may comprise at least XnAP ID of the target base station, an RRCrelease message or a cause value.

For the RRC connection resume procedure, based on receiving the retrieveUE context response message, the target base station may send an RRCresume message to the UE. The RRC resume message may comprise at leastone of radio bearer configuration parameters, cell group configurationparameters for MCG and/or SCG, measurement configuration parameters orsk counter wherein the sk counter is used to derive a security key ofsecondary base station based on K_(gNB).

Based on receiving the retrieve UE context failure message, the targetbase station may send an RRC release message to the UE. For example,based on the retrieve UE context failure message comprising the RRCrelease message, the target base station may send the RRC releasemessage to the UE. Based on receiving the retrieve UE context failuremessage, the target base station may send an RRC setup message or an RRCreject message. Based on receiving the retrieve UE context failuremessage, the target base station may not send any response message tothe UE.

Based on receiving the RRC resume message, the UE may stop the timerT319 and T380. Based on receiving the RRC resume message, the UE mayrestore mater cell group configuration parameters, secondary cell groupconfiguration parameters and PDCP configuration parameters in the UEinactive AS context. Based on restoring the master cell groupconfiguration parameter and/or the secondary cell group configurationparameters, the UE may configure SCells of MCG and/or SCG by configuringlower layers to consider the restored MCG and/or SCG SCells to be indeactivated state, discard the UE inactive AS context and release thesuspend configuration parameters.

Based on receiving the cell group configuration parameters in the RRCresume message, the UE may perform cell group configuration of MCGand/or SCG. Based on receiving the radio bearer configuration parametersin the RRC resume message, the UE may perform radio bearerconfiguration. Based on the sk counter in the RRC resume message, the UEmay perform to update the security key of secondary base station.

FIG. 18 illustrates an example of an RRC connection resume procedure. AUE in RRC connected state may transmit and receive data to/from a firstbase station (a source base station) via a cell 1. The first basestation may determine to transit a UE in RRC connected state to RRCinactive state. Based on the determining, the base station may send anRRC release message comprising the suspend configuration parameters.Based on receiving the RRC release message comprising suspendconfiguration parameters, the UE may store in the UE inactive AS Contextthe current K_(gNB) and K_(RRCint) keys, a robust header compression(ROHC) state, stored QoS flow to DRB mapping rules, the C-RNTI used inthe source PCell, the cell identity and the physical cell identity ofthe source PCell, and all other parameters configured except for theones within reconfiguration with sync and serving cell configurationcommon parameters in SIB. The UE may suspend all SRB(s) and DRB(s)except for SRB0. Based on receiving the RRC release message comprisingsuspend configuration parameters, the UE may start a timer T380, enterRRC inactive state, perform cell selection procedure. Based on the cellselection procedure, the UE may select a cell 2 of a second base station(a target base station). The UE in RRC inactive state may initiate anRRC connection resume procedure. The UE may perform the unified accesscontrol procedure. Based on the unified access control procedure, the UEmay consider access attempt for the RRC connection resume procedure asallowed. The UE may apply the default L1 parameter values as specifiedin corresponding physical layer specifications, except for theparameters for which values are provided in SIB1, apply the default SRB1configuration, apply the CCCH configuration, apply the time alignmenttimer common included in SIB1, apply the default MAC cell groupconfiguration, start a timer T319 and initiate transmission of an RRCresume request message. Based on initiating the transmission of the RRCresume request message, the UE may restore RRC configuration parametersand security keys from the UE inactive AS context. For example, the UEmay restore the RRC configuration parameters and the K_(gNB) andK_(RRCint) keys from the stored UE Inactive AS context except for themaster cell group configuration parameters, MR-DC related configurationparameters (e.g., secondary cell group configuration parameters) andPDCP configuration parameters. Based on current (restored) K_(gNB) ornext hop (NH) parameters associated to the stored NCC value, the UE mayderive a new key of a base station (K_(gNB)). Based on the new key ofthe base station, the UE may derive security keys for integrityprotection and ciphering of RRC signalling (e.g., K_(RRCenc) andK_(RRCint) respectively) and security keys for integrity protection andciphering of user plane data (e.g., K_(UPint) and the K_(UPenc)respectively). Based on configured algorithm and the K_(RRCint) andK_(UPint), the UE (RRC layer) may configure lower layers (e.g., PDCPlayer) to apply integrity protection for all radio bearers except SRB0.Based on configured algorithm and the K_(RRCenc) and the K_(UPenc), theUE may configure lower layers (e.g., PDCP layer) to apply ciphering forall radio bearers except SRB0. For communication between the UE and thebase station, the integrity protection and/or the ciphering may berequired. Based on the integrity protection and/or the ciphering, the UEmay be able to transmit and receive data to/from the second basestation. The UE may use the restored RRC configuration parameters totransmit and receive the data to/from the second base station. Based oninitiating the transmission of the RRC resume request message, the UEmay re-establish PDCP entities for SRB1, resume SRB1 and submit the RRCresume request message to lower layers. Based on receiving the RRCresume request message, the second base station may check whether the UEcontext of the UE is locally available. Based on the UE context beingnot locally available, the second base station may perform the retrieveUE context procedure by sending the retrieve UE context request messageto the first base station (the last serving base station) of the UE. Theretrieve UE context request message may comprise at least one of resumeidentity, resume MAC-I, or the resume cause. based on receiving theretrieve UE context request message, the first base station may checkthe retrieve UE context request message. If the first base station isable to identify the UE context by means of the UE context ID, and tosuccessfully verify the UE by means of the resume MAC-I and decides toprovide the UE context to the second base station, the first basestation may respond to the second base station with the retrieve UEcontext response message. Based on receiving the retrieve UE contextresponse message, the second base station may send an RRC resume messageto the UE. Based on receiving the RRC resume message, the UE may restoremater cell group configuration parameters, secondary cell groupconfiguration parameters and PDCP configuration parameters in the UEinactive AS context. Based on restoring the master cell groupconfiguration parameter and/or the secondary cell group configurationparameters, the UE may configure SCells of MCG and/or SCG by configuringlower layers to consider the restored MCG and/or SCG SCells to be indeactivated state, discard the UE inactive AS context and release thesuspend configuration parameters. The UE may transmit and receive datavia the SCells and/or SCGs.

The RRC resume message may comprise at least one of cell groupconfiguration parameters of MCG and/or SCG, radio bearer configurationparameters or AS security key parameters (e.g., sk counter).

FIG. 19 illustrates an example of an RRC connection resume procedurewith anchor relocation. A UE (e.g., a wireless device) may be in RRCinactive state. An old base station (e.g., anchor base station or firstbase station or source base station) may sends an RRC release messagerequesting to suspend RRC connection. The RRC release message mayrequest the UE to be in RRC inactive state. For example, the anchor basestation may send the RRC release message comprising the suspendconfiguration parameters to the UE. Based on sending the RRC releasemessage, the anchor base station may store current UE configurationparameters and the suspend configuration parameters into UE context(e.g., UE inactive AS context) and transition to an RRC inactive state.Based on receiving the suspend configuration parameters, the UE mayenter to an RRC inactive state. The suspend configuration parameters maycomprises a resume identity of the UE (e.g., I-RNTI). Based on receivingthe RRC release message, the UE may store current configurationparameters and the suspend configuration parameters. Based on receivingthe RRC release message, the UE may suspend all SRB(s) and DRB(s) exceptfor SRB0, and transition (enter) to an RRC inactive state. The UE mayperform a cell selection procedure. Based on the cell selectionprocedure, the UE may select a cell of a new base station (e.g.,non-anchor base station or target base station or second base station).The UE may perform an RRC connection resume procedure by sending an RRCresume request message to the new base station via the cell. The RRCresume request message may comprise the resume identity and the resumecause. The new base station may send a retrieve UE context requestmessage to the anchor base station to request UE context of the UE,wherein the retrieve UE context request message may comprise the resumeidentity and the resume cause. Based on the retrieve UE context requestmessage, the anchor base station may determine to perform anchorrelocation by sending the retrieve UE context response messagecomprising the UE context to the new base station. Based on the retrieveUE context response message, the new base station may send an RRC resumemessage to the UE. Based on the RRC resume message, the UE may resumethe suspended SRBs and DRBs, transition to an RRC connected state andsend an RRC resume complete message to the new base station. The anchorbase station may buffer downlink user data of the UE. The new basestation may send user plane address for forwarding the downlink userdata. The anchor base station may send the downlink user data to the newbase station via the address. An existing path fortransmitting/receiving control signalling of the UE (e.g., N2 interface)may be between the anchor base station and AMF. An existing path fortransmitting/receiving user data of the UE (e.g., N3 interface) may beestablished between the anchor base station and UPF. Based on the anchorrelocation, the path (and resource) for transmitting/receiving controlsignalling and user data may need to be updated as between the new basestation and AMF/UPF. For the updating the path, the new base station mayperform a path switch procedure by sending a path switch request messageto AMF. The path switch request message may comprise new addresses ofthe new base station for transmitting/receiving control signalling anduser data of the UE, and PDU session information comprising PDU sessionidentities. Based on the path switch request message, the AMF may updatethe path for transmitting/receiving control signalling of the UE. Basedon the path switch request message, the AMF may perform a PDU sessionupdate procedure with SMF. The SMF may perform a PDU sessionmodification with UPF. Based on the procedure, the SMF and UPF mayupdate the path (and resource) for transmitting/receiving the user dataof the UE. The AMF may send a path switch response message to the newbase station. Based on receiving the path switch response message, thenew base station may update the path for transmitting/receiving controlsignalling and user data of the UE, and send a UE context releasemessage to the anchor base station. Based on the UE context releasemessage, the anchor may release the UE context. Based on the updatedpath, the new base station may forward uplink user data from the UE tothe UPF and forward downlink data from the UPF to the UE.

FIG. 20 illustrates an example of an RRC connection resume procedurewithout anchor relocation. A UE (e.g., a wireless device) may perform anRRC connection resume procedure by sending an RRC resume request messageto the new base station via the cell. The RRC resume request message maycomprise the resume identity and the resume cause wherein the resumecause is RNA update. The new base station may send a retrieve UE contextrequest message to the anchor base station wherein the retrieve UEcontext request message may comprise the resume identity and the resumecause, RNA update. The resume cause, RNA update may indicate that thereis no user data transmission. Based on the resume cause, RNA update, theanchor base station may determine not to perform anchor relocation. andthe resume cause, RNA update. Based on the determining, the anchor basestation may send a retrieve UE context failure message comprising an RRCrelease message to the new base station. The RRC release message maycomprise the suspend configuration parameters or downlink data. Based onreceiving the retrieve UE context failure message, the new base stationmay forward the RRC release message to the UE. Based on receiving theRRC release message, the UE may transition to either an RRC inactivestate or an RRC idle state.

FIG. 21 illustrates an example of a control plane early datatransmission procedure. A UE (e.g., a wireless device) in an RRC idlestate may send an RRC early data request message comprising a NASmessage wherein the NAS message may comprise uplink data and NAS releaseassistance information (or release assistance indication). The NASrelease assistance information (RAI) may indicate expected datatransmission information. The RAI (e.g., the expected data transmissioninformation) may comprise at least one of: (a) no further uplink and nofurther downlink data transmission is expected; (b) a single downlinkdata transmission and no further uplink data transmission is expected;or (c) more than single uplink or downlink data transmission isexpected.

Based on receiving the RRC early data request message, a new basestation may send an initial UE message comprising the NAS message to anAMF. The AMF may determine a PDU session contained in the NAS message.Based on the determining, the AMF may send the PDU session identity (ID)and the uplink data to the SMF and the SMF may forward the uplink datato the UPF. The UPF may forward downlink data of the UE to the SMF andthe SMF may forward the downlink data to the AMF. The AMF may send a NASmessage to the UE wherein the NAS message may comprise the downlink dataof the UE. Based on having the downlink data, the AMF may send adownlink (DL) NAS transport message comprising the NAS message to thenew base station. Based on not having the downlink data, the AMF maysend a connection establishment indication indicating that there is nopending downlink data. The new base station may send an RRC early datacomplete message comprising the NAS message to the UE. Based on the RRCearly data complete message, the UE may transition to an RRC idle stateor keep the RRC state based on the RRC state being an RRC idle state.

FIG. 22 illustrates an example of a user plane early data transmissionprocedure with anchor relocation. A UE (e.g., a wireless device) may bean RRC idle state with suspending RRC connection as well as a CM idlestate with suspending RRC connection. An old base station (e.g., ananchor base station) may have UE context of the UE. Based on the RRCstate of the UE being the RRC idle state with suspended RRC connection,the anchor base station may have no connection fortransmitting/receiving control signaling of the UE with an AMF and/or noconnection for transmitting/receiving user data of the UE with an UPF.Based on the RRC state of the UE being the RRC inactive state, theanchor base station may have them. The UE may send an RRC resume requestmessage to a new base station (e.g., a target base station). The RRCresume request message may comprise UL data and/or AS RAI (e.g., RAI ofthe AS layer). The UE may send the RRC resume message via CCCH, the ULdata via DTCH and the AS RAI via MAC CE. The UE may multiplex the RRCresume message, the UL data and the AS RAI. The AS RAI may comprise atleast one of: (a) no further uplink and no further downlink datatransmission is expected; (b) a single downlink data transmission and nofurther uplink data transmission is expected; or (c) more than singleuplink or downlink data transmission is expected.

Based on receiving the RRC resume request message, the new base stationmay send a retrieve UE context request message to the old base station.Based on the retrieve UE context message, the anchor base station maysend a retrieve UE context response comprising UE context of the UE.Based on receiving the retrieve UE context response, the UE may send aN2 resume request message or a path switch request message requesting toresume N2 and N3 connection of the UE and/or to switch a path of N2 andN3 connection to an AMF. The N2 connection may indicate a connection onN2 interface between an AMF and a base station and The N3 connection mayindicate a connection on N3 interface between an UPF and a base station.For the N3 connection, the UE may include a PDU session information(e.g., PDU session identity) associated to the uplink data in the N2resume request message or the path switch request message. Based on theAS RAI, the UE may send an immediate suspend indication requesting tosuspend RRC connection of the UE via the N2 resume request message. Forexample, the UE mas send the immediate suspend indication via the N2resume request message based on the AS RAI indicating either: (a) nofurther uplink and no further downlink data transmission is expected; or(b) a single downlink data transmission and no further uplink datatransmission is expected.

Based on receiving the N2 resume request message, the AMF may requestthe SMF to resume the PDU session for the uplink data and the SMF mayrequest the UPF to create the tunnel information for the UE and updatethe downlink path. The AMF may send a N2 resume response message and/ora path switch response message to the new base station. Based on the N2resume response message and/or the path switch response message, the newbase station may update(switch) the path of the N2 connection and the N3connection, and send a UE context release message to the anchor basestation. Based on the UE context release message, the anchor may releasethe UE context. Based on the updated path, the new base station mayforward uplink user data from the UE to the UPF and forward downlinkdata from the UPF to the UE. The new base station may perform a suspendprocedure requesting to suspend RRC connection of the UE by sending a N2suspend request message to the AMF. The AMF may determine to suspend RRCconnection of the UE based on the immediate suspend indication. Based ondetermining to suspend the RRC connection, the AMF may send a PDUsession update message indicating to suspend the RRC connection of theUE to the SMF. The SMF may send a PDU session modification messageindicating to suspend the RRC connection. Based on determining tosuspend the RRC connection, the AMF may send a N2 suspend responsemessage to the new base station. Based on the N2 suspend responsemessage, the new base station may send an RRC release message requestingto suspend RRC connection of the UE to the UE wherein the RRC releasemessage may comprise the downlink data. Based on sending the RRC releasemessage, the new base station may store the current configurationparameters of the UE and/or the suspend configuration parameters.

For small data transmission using a user plane EDT procedure, uplink anddownlink data transmission may be delayed based on an anchor basestation being different from a new base station. The delay may becontinued until a path switch procedure is completed. In the example ofFIG. 22 , the anchor base station may perform an anchor relocation bysending a retrieve UE context response comprising UE context of the UE.The anchor relocation may trigger the path switch procedure (e.g., thepath switch request message and the path switch response message or theN2 resume request procedure (e.g., the N2 resume request message and theN2 resume response message). Based on completing the path switchprocedure or the N2 resume request procedure (e.g., based on receivingthe path switch response message or the N2 resume response message), thenew base station may transmit uplink data to the UPF and receivedownlink data of the UE from the UPF.

FIG. 23 illustrates an example of optimal path for data transmission inmobility of a wireless device. A UE (e.g., a wireless device) at time T1may be in RRC connected state and then transition to an RRC inactive orRRC idle state with suspending RRC connection based on receiving an RRCrelease message from a first base station at time T2. The first basestation may be an anchor base station by storing the UE context of theUE. Based on an RRC state being the RRC inactive state, a connection(e.g., N3 connection) for a path (A) may be kept as connected. Based onan RRC state being the RRC idle state with suspending RRC connection, aconnection (e.g., N3 connection) for a path (A) may be released and thefirst base station and a UPF may store information for the connection(e.g., address for the connection). The UE in the RRC inactive state orthe RRC idle state with suspending RRC connection may perform a cellselection procedure. Based on the cell selection procedure, the UE mayselect a cell of a second base station and camp on the cell. The UE mayperform an RRC resume procedure by sending an RRC resume procedure attime T3. For uplink data and downlink data transmission/reception of theUE, a most direct path (B1) may be considered as optimal path. To usethe most direct path (B1), the anchor (base station) of the UE may needto be relocated from the first base station to the second base stationby sending UE context from the first base station to the second basestation. The anchor relocation may trigger a path switch procedureindicating the anchor relocation to core network entities (e.g., AMF andUPF). Based on completing of the path switch procedure, uplink data anddown data may be transmitted/received via the path (B1). For uplink dataand downlink data transmission/reception via path (B1), signaling forthe anchor relocation procedure and the path switch procedure may benecessary. As a result, data transmission/reception may be delayed untilcompletion of the anchor relocation procedure and the path switchprocedure. The UE may have small amount of uplink/down data. As will bediscussed in greater detail below, transmission/reception via anindirect path (B2) may be optimal in some scenarios. For example, ifthere is a small amount of data to be transmitted, then the signalingand delay associated with switching to path (B1) may not be justified.

In existing technologies, an old base station (e.g., anchor basestation) that stores/keeps a context of the wireless device in an RRCinactive state may receive a retrieve UE context request message fromthe new base station. In response to the request, the old base stationmay determine to relocate the context to the new base station. If thesize of data to communicate for the wireless device is small, relocatingcontext of the wireless device from an old base station to a new basestation may not be efficient. Relocation of context may increasesignaling and latency of the data transmission.

Based on the retrieve UE context request message (e.g., comprisinguplink data), the old base station may determine to keep the context. Inexisting technologies, the old base station may send an RRC releasemessage to the wireless device via the new base station based on thedetermining. However, after sending the RRC release message, the oldbase station may receive downlink data from the core network (e.g.,downlink data for the wireless device). To send the downlink data to thewireless device, the old base station may need to perform a pagingprocedure, which increases signaling. Existing technologies may increaseinefficient signaling and data transmission delay.

Example embodiments of the present disclosure are directed to anenhanced procedure for transmission of small amounts of data. Whereasexisting technologies continue to have high latency and signalingoverheads for data transmission, example embodiments leverage (AS) RAIand downlink data information to more efficiently transmit/receive smalldata.

In an example embodiment, a new base station may send to an anchor basestation a retrieve UE context request message comprising assistanceinformation (e.g., small data transmission assistance information).Based on the assistance information, the anchor base station maydetermine whether to relocate a context of a wireless device. This mayreduce signaling and latency of data transmission/reception due torelocating of the context of the wireless device. Based on theassistance information, the anchor base station may determine whether towait to receive downlink data of the wireless device from a core networkentity. Based on determining to wait to receive the downlink data, theanchor base station may postpone to send an RRC release message for thewireless device until receiving downlink data. This may reduceunnecessary signaling for example, due to paging procedure whichincreases latency of downlink data transmission to the wireless device.Based on determining not to wait for the downlink data, the anchor basestation may send an RRC release message to the wireless device via thenew base station. This may decrease time of the small data transmissionwhich reduces power consumption of the wireless device.

In existing technologies, a base station which has data of a wirelessdevice to transmit to another base station may perform a tunnelestablishment procedure (e.g., tunnel address request and response)while postponing sending of the data until a user plane tunnel isestablished. A new base station that receives uplink data (e.g., smalldata) and an RRC request message from a wireless device may send aretrieve UE context request message to an old base station (e.g., anchorbase station) that stores/keeps the context of the wireless device. Inexisting technologies, the new base station may postpone sending of theuplink data to the anchor base station until the user plane tunnel forthe small uplink data is established, causing delay of sending theuplink data to an application server via a core network entity. Thedelayed uplink data may cause delay of downlink data, in response to theuplink data, which is sent by the application server to the anchor basestation. The wireless device may need to monitor downlink channel untilreceiving the delayed downlink data. This may increase power consumptionof the wireless device.

In such scenario, the anchor base station receiving the downlink datafrom the core network entity may postpone sending of the downlink datato the new base station until a user plane tunnel for the downlink datais established. This may cause signaling and latency for transmission ofthe downlink data. The wireless device may need to monitor downlinkchannel until receiving the delayed downlink data. This may increasepower consumption of the wireless device. Example embodiments enable abase station to send data to another base station without the delay forestablishing user tunnel between base stations.

In an example embodiment, a new base station may send to an anchor basestation a retrieve UE context request message comprising uplink data(e.g., when size of the uplink data is small). This may reduce the delayof uplink data transmission to the core network entity. In an exampleembodiment, the anchor base station may send to the new base station aretrieve UE context failure message comprising downlink data whenreceiving the downlink data from a core network entity. This may reducethe delay of downlink data transmission to a wireless device.

FIG. 24 illustrates an example diagram showing an enhanced procedure forsmall data transmission without anchor relocation in RRC inactive state.A first base station (e.g., old base station or anchor base station orsource station) may receive a release assistance information (RAI) for awireless device (a UE) from a second base station (e.g., a new basestation or non-anchor base station or a target base station). Based onthe RAI, the first base station may determine whether to perform anchorrelocation for the UE or not. Based on determining to perform anchorrelocation, the first base station may send a retrieve UE contextresponse message comprising UE context of the UE to the second basestation. Based on determining not to perform anchor relocation (e.g.,determining to keep anchor), the first base station may send a retrieveUE context failure message comprising an RRC release message to thesecond base station.

In an example of FIG. 24 , RAI may indicate that a downlink datatransmission is expected (e.g., a single downlink data transmission andno further uplink data transmission is expected). Based on the RAI, thefirst base station may wait for downlink data from the UPF. Based on theRAI, the first base station may determine not to perform anchorrelocation. Based on receiving the downlink data, the first base stationmay send a retrieve UE context failure message comprising an RRC releasemessage wherein the RRC release message may comprise the downlink data.

In an example of FIG. 24 , RAI may comprise expected data transmissioninformation. The expected data transmission information may comprise atleast one of: (a) no further uplink and no further downlink datatransmission is expected; (b) a single downlink data transmission and nofurther uplink data transmission is expected; or (c) more than singleuplink or downlink data transmission is expected.

In an example of FIG. 24 , RAI may indicate that no further datatransmission is expected (e.g., no further uplink and no furtherdownlink data transmission is expected). Based on the RAI, the firstbase station may not wait downlink data from the UPF and send theretrieve UE context failure message comprising the RRC release message.

In an example of FIG. 24 , RAI may indicate neither that no datatransmission is expected nor that single downlink data transmission isexpected (e.g., more than single uplink or downlink data transmission isexpected). Based on the RAI, the first base station may determine toperform anchor relocation by sending the retrieve UE context responsemessage comprising UE context of the UE.

In an example of FIG. 24 , the first base station may not receive RAI.Based on not having RAI, the first base station may determine to performanchor relocation by sending the retrieve UE context response messagecomprising UE context of the UE.

In an example of FIG. 24 , based on receiving the retrieve UE contextfailure message, the second base station may forward the RRC releasemessage to the UE. Based on receiving the RRC release message, the UEmay transition to an RRC inactive or an RRC idle state (with suspendingRRC connection).

FIG. 25 illustrates an example of an enhanced procedure for mobileoriginated data transmission without anchor relocation in RRC inactivestate. A wireless device or UE may be in a CM connected state and an RRCinactive state. An old base station (e.g., anchor base station or firstbase station or source base station) may have stored UE context in UEinactive AS context. The UE may have small uplink data. Based on thesmall uplink data, the UE may determine to perform a user plane EDTprocedure. Based on the determining, the UE may send an RRC resumerequest message, uplink (UL) data and (AS) RAI to a new base station(e.g., non-anchor base station or target base station or second basestation). Based on receiving the UL data, the first base station maysend the UL data to the UPF. For example, based on receiving the ULdata, the first base station may send the UL data via the N3 connectionof the UE to the UPF. The first base station may be wait for downlinkdata from the UPF based on the RAI indicating that a downlink datatransmission is expected (e.g., a single downlink data transmission andno further uplink data transmission is expected). Based on receiving thedownlink data, the first base station may send a retrieve UE contextfailure message comprising an RRC release message wherein the RRCrelease message may comprise the downlink data. RAI may indicate that nofurther data transmission is expected (e.g., no further uplink and nofurther downlink data transmission is expected). Based on the RAI, thefirst base station may not wait downlink data from the UPF and send theretrieve UE context failure message comprising the RRC release message.Based on receiving the retrieve UE context failure message, the secondbase station may forward the RRC release message to the UE wherein theRRC release message may comprise the downlink data. Based on receivingthe RRC release message, the UE may transition to an RRC inactive or anRRC idle state (with suspending RRC connection).

FIG. 26 illustrates an example of an enhanced procedure for mobileterminated data transmission without anchor relocation in RRC inactivestate. The data may be small data. A wireless device or UE may be CMconnected state and an RRC inactive state. An old base station (e.g., ananchor base station, a first base station) may have stored UE context inUE inactive AS context. The first base station may receive smalldownlink data. Based on the small downlink data, the first base stationmay determine to perform a user plane EDT procedure. Based on thedetermining, the first base station may broadcast a paging messagecomprising mobile terminated (MT) EDT indication via one or more cellsof the first base station and send the paging message to one or morebase stations in RNA area. The base stations may broadcast the pagingmessage via one or more cells of each base station. The UE may receivethe paging message via a cell of a new base station (e.g., a new basestation, a target base station, a second base station). Based on the MTEDT indication of the paging message, the UE may determine to perform auser plane EDT procedure. Based on the determining, the UE may send anRRC resume request message and (AS) RAI to the second base station.Based on receiving the RRC resume request message, the second basestation may send a retrieve UE context request message comprising theRAI. The RAI may indicate that no further data transmission is expected(e.g., no further uplink and no further downlink data transmission isexpected). Based on the RAI, the first base station may send theretrieve UE context failure message comprising the RRC release messagewherein the RRC release message may comprise the downlink data. Based onreceiving the retrieve UE context failure message, the second basestation may forward the RRC release message to the UE. Based onreceiving the RRC release message, the UE may transition to an RRCinactive or an RRC idle state (with suspending RRC connection).

In an example, RAI may comprise (expected) amount of uplink and/ordownlink data. Based on the RAI, the first base station may determinewhether to perform anchor relocation or not. For example, based on theamount of uplink and/or downlink data being smaller than a datathreshold, the first base station may determine not to perform anchorrelocation. For example, based on the amount of uplink and/or downlinkdata being larger than a data threshold, the first base station maydetermine not to perform anchor relocation. For example, based on sum ofuplink data and downlink data being smaller than the data threshold, thefirst base station may determine not to perform anchor relocation. Thesecond base station (and/or the UE) may configure or send the datathreshold to the first base station. The second base station (and/or theUE) may determine the data threshold.

In an example, the data threshold may comprise a data threshold foruplink data transmission and a data threshold for downlink transmission.The data threshold for uplink data transmission may be used for uplinkdata and the data threshold for downlink data transmission may be usedfor downlink data. For example, based on the amount of uplink beingsmaller than the data threshold for uplink data transmission and theamount of downlink data being smaller than the data threshold fordownlink data transmission, the first base station may determine not toperform anchor relocation. For example, based on either the amount ofuplink being larger than the data threshold for uplink data transmissionor the amount of downlink data being larger than the data threshold fordownlink data transmission, the first base station may determine toperform anchor relocation. In an example, the RAI may comprise the datathreshold.

In an example, a second base station (and/or a UE and/or a first basestation) may determine the data threshold based on at least one ofsignaling quality between the UE and the second base station, UEcapability, expected arrival time of expected uplink/downlink data orexpected resource for expected data transmission (e.g., expected time oramount of radio frequency resource or transmission power). For example,the expected resource for expected data transmission may be determinedbased on the signaling quality and/or the UE capability. The UE maysends the UE capability, expected arrival time of expecteduplink/downlink data and/or the expected resource for expected datatransmission to the second base station and/or the first base station.

In an example, the RAI may comprise at least one of signaling qualitybetween the UE and the second base station, UE capability, expectedarrival time of expected uplink/downlink data or expected resource forexpected data transmission (e.g., expected time or amount of radiofrequency resource frequency or transmission power).

In an example, RAI may comprise at least one of: data radio beareridentity associated with data transmission; or application informationassociated with data transmission. For example, the UE and/or the firstbase station may configure a data radio bearer for small datatransmission. the UE and/or the first base station may configureapplication information (e.g., application identifier) for small datatransmission. Based on the data radio bearer identity or the applicationinformation, the first base station may determine not to perform anchorrelocation.

In an example of FIG. 25 and/or FIG. 26 , based on sending the retrieveUE context request message, the second base station may start a timerwith a timer value. The second base station may determine the timervalue based on the RAI. For example, the second base station maydetermine the timer value based on downlink data being expected and/orexpected arrival time of the downlink data (e.g., round trip time ofdata transmission). The timer value may be preconfigured or determinedin a UE and/or a base station. For example, the timer value may bepreconfigured or determined based on application information and/or dataradio bearer identity. The second base station may start the timer withthe timer value based on sending the retrieve UE context requestmessage. Based on receiving the response message, the second basestation may stop the timer wherein the response message may comprise atleast of a retrieve UE context response message or a retrieve UE contextfailure message. Based on expiry of the timer, the second base stationmay send the retrieve UE context request message to the first basestation again. Based on expiry of the timer, the second base station maydetermine a failure to receive the response message. Based on thedetermining, the second base station may send an RRC reject message tothe UE in response of the RRC resume request message.

In an example of FIG. 25 and/or FIG. 26 , the retrieve UE contextrequest message may comprise the timer value. Based on receiving thetimer value, the first base station may start a timer with the timervalue. Based on sending a response message for the retrieve UE contextmessage, the first base station may stop the timer. For example, basedon receiving downlink data, the first base station may send the responsemessage (e.g., a retrieve UE context failure message). Based on expiryof the timer, the first base station may send the response message. Forexample, RAI may indicate that a downlink data transmission is expected(e.g., a single downlink data transmission and no further uplink datatransmission is expected). Based on the RAI, the first base station maywait for the downlink data. The first base station may start the timerwith the timer value. Based on expiry of the timer, the first basestation may determine anchor relocation. Based on the determining, thefirst base station may send a retrieve UE context response messagecomprising UE context of the UE.

In an example of FIG. 25 and/or FIG. 26 , RAI may indicate that adownlink data transmission is expected (e.g., a single downlink datatransmission and no further uplink data transmission is expected). Basedon the RAI, the first base station may send a message indicating thatdownlink data is expected. Based on receiving the message, the secondbase station may wait for response of the retrieve UE context requestmessage and the downlink data. Based on receiving the message, thesecond base station may stop the timer and restart the timer with thetimer value.

In an example of FIG. 25 and/or FIG. 26 , the first base station mayreceive downlink data from the UPF. The first base station may waitadditional downlink data from the UPF. For example, RAI may compriseamount of (expected) downlink data. Based receiving first downlink datafrom the UPF and the amount of the first downlink data be smaller thanthe amount of expected downlink data, the first base station maydetermine to wait additional downlink data from the UPF. Based on thedetermining, the first base station may send a message comprising thefirst downlink data to the second base station. The message may indicateindicating that additional downlink data is expected. Based on receivingthe message, the second base station may wait for response of theretrieve UE context request message and the additional downlink data.Based on receiving the message, the second base station may stop thetimer and restart the timer with the timer value. Based on receiving themessage comprising the first downlink data, the second base station maystore the first downlink data in buffer. Based on receiving the messagecomprising the first downlink data, the second base station may send aradio message comprising the first downlink data to the UE. The radiomessage may indicate the additional downlink data is expected. Based onreceiving the radio message, the UE may wait for the additional downlinkdata and keep monitoring downlink channel of the second base station.Based on receiving a second downlink data and sum of the first downlinkdata and the second downlink data being equal to the data threshold (orlarger than the data threshold), the first base station send a retrieveUE context failure message comprising an RRC release message wherein theRRC release message may comprise the second downlink data and/or thefirst downlink data. Based on receiving the RRC release message, thesecond base station may forward the RRC release message to the UE.

In an example, the first base station may have pending downlink databased on receiving the retrieve UE context request message. Based on thepending downlink data, the first base station may determine to performanchor relocation. For example, based on the amount of the pendingdownlink data being smaller than the data threshold, the first basestation may determine not to perform anchor relocation. For example,based on the amount of the pending downlink data being larger than thedata threshold, the first base station may determine to perform anchorrelocation. The first base station may determine not to perform anchorrelocation based on at least one of the RAI or the pending downlinkdata.

In an example, the UE in an RRC inactive state or an RRC idle state withsuspending RRC connection may have uplink data wherein the uplink datamay be a small data to transmit via control plane interface. Based onthe uplink data being the small data to transmit via control planeinterface, a NAS message comprise the small data. The UE may determine auser plane EDT procedure. The UE may send an RRC resume request message,the NAS message comprising the uplink data and (AS) RAI. Based onreceiving the RRC resume request message, the second base station maysend a retrieve UE context request message comprising the NAS messageand the RAI to the first base station. Based on receiving the retrieveUE context request message, the first base station may send the NASmessage an AMF. Based on the RAI, the first base station may determinenot to perform anchor relocation. The first base station may wait fordownlink data from the AMF based on the RAI wherein a NAS message maycomprise the downlink data. Based on receiving the downlink data, thefirst base station may send a retrieve UE context failure messagecomprising an RRC release message wherein the RRC release message maycomprise the NAS message. Based on receiving the RRC release message,the second base station may forward the RRC release message to the UE.

In existing technologies, a connection between a base station and corenetwork entities (e.g., AMF and UPF) may be suspended when a wirelessdevice is in an RRC idle state with suspending a RRC connection whilethe connection is established when a wireless device is in an RRCinactive state. The AMF may determine whether to transition a wirelessdevice to an RRC connected state or not when receiving from a basestation a request to resume the suspended connection. An AMF receivingfrom a base station a request to resume suspended connection maydetermine to transition a wireless device to an RRC connected state whenthe base station receives RAI indicating small amount of data. Thetransitioning to the RRC connected state may cause signaling overheadsto update path/connection between the base station and core networkentities. Transmission and reception may be delay until thepath/connection is updated. The delay may cause power consumption of thewireless device.

For example, based on an RRC state of a UE being an RRC idle state withsuspending RRC connection and receiving downlink data, the downlink datamay be pending in an AMF or an UPF not a base station. For example,based on the downlink data being control plane data, the downlink datamay be pending in the AMF. Based on the downlink data being user planedata, the downlink data may be pending in the UPF. The base station maynot have downlink data information for the pending downlink data basedon the downlink data pending in the AMF or the UPF. The base stationdetermining to provide contexts of a UE to new base station withoutknowing the pending downlink data in the core network entities beingsmall amount of data. The determining may cause signaling overheads toupdate path/connection between the base station and the core networkentities. Transmission and reception may be delay until thepath/connection is updated. The delay may cause power consumption of thewireless device.

In an example embodiment, an old base station storing contexts of awireless device may send RAI to AMF when receiving from a new basestation a retrieve UE context request message comprising the RAI. Basedon the RAI, the AMF may determine whether to perform anchor relocationor not. Based on the determining, the AMF may indicate the determiningto the old base station. Based on the determining, the old base stationmay keep or provide the contexts of the wireless device. This may avoidunnecessary signals and delay due to anchor relocation between basestations and updating path/connection between a base station and corenetwork entities. The reduce delay may reduce power consumption of awireless device.

FIG. 27 illustrates an example diagram showing an enhanced procedure fordata transmission without anchor relocation in RRC idle state. The datamay be small data. A first base station (e.g., old base station oranchor base station or source base station) may receive releaseassistance information for a wireless device (a UE) from a second basestation (e.g., new base station or non-anchor base station or targetbase station). Based on an RRC state of a wireless device being an RRCinactive state, the first base station may determine whether to performanchor relocation based on the RAIFIG. 24. Based on an RRC state of awireless device not being an RRC inactive state (e.g., an RRC state ofthe wireless device being an RRC idle state with suspending RRCconnection, the first base station may send the RAI to an AMF. Based onthe RAI, the AMF may determine whether to perform anchor relocation ornot.

FIG. 28 illustrates an example of an enhanced procedure for mobileoriginated data transmission without anchor relocation in RRC idlestate. A wireless device or UE may be in an RRC idle state withsuspending RRC connection. An old base station (e.g., anchor basestation or first base station or source base station) may have stored UEcontext. The UE may have small uplink data. Based on the small uplinkdata, the UE may determine to perform a user plane EDT procedure. Basedon the determining, the UE may send an RRC resume request message,uplink (UL) data and (AS) RAI to a new base station (e.g., non-anchorbase station or target base station or second base station). Based onreceiving the UL data, the first base station may send the UL data tothe UPF. For example, based on receiving the UL data, the first basestation may send the UL data via the N3 connection of the UE to the UPF.Based on an RRC state of the UE being an RRC idle state with suspendingRRC connection, the first base station may send a N2 resume requestmessage (or a path switch request message) comprising the RAI to an AMF.Based on the RAI, the AMF may determine whether to perform anchorrelocation in the first base station. The AMF may determine whether toperform anchor relocation in the first base station based on at leastone of the RAI and downlink data information for pending downlink data.The AMF may request downlink data information to a SMF and/or an UPF.Based on receiving the N2 resume request message or the path switchrequest message, the AMF may perform an PDU session update procedurewith the SMF and the SMF may perform an PDU session modificationprocedure with the UPF. Based on the PDU session update procedure andthe PDU session modification procedure, the AMF may obtain downlinkinformation for pending downlink data in the SMF and/or the UPF. Forexample, via the PDU session update procedure and the PDU sessionmodification procedure, the AMF may request downlink data informationfor pending downlink data and the SMF or the UPF may send the downlinkdata information for pending downlink data. The AMF may determine not toperform anchor relocation based on at least one of the RAI or thedownlink information. Based on the determining, the AMF may send a N2resume response message (or a path switch response message) to the firstbase station wherein the N2 resume response message may comprise asuspend indication requesting to suspend RRC connection. Based onreceiving the N2 resume response message, the first base station maysend a retrieve UE context failure message comprising an RRC releasemessage. Based on receiving the N2 resume response message and the RAIindicating that a downlink data transmission is expected (e.g., a singledownlink data transmission and no further uplink data transmission isexpected), the first base station may wait for the downlink data. Basedon receiving the downlink data, the first base station may send aretrieve UE context failure message comprising an RRC release messagewherein the RRC release message may comprise the downlink data. Based onreceiving the RRC release message, the second base station may forwardthe RRC release message to the UE.

In an example of FIG. 28 , the AMF may send the RAI to the SMF and/orthe UPF based on receiving the RAI from the first base station. Based onreceiving the RAI, the SMF or the UPF may determine whether to performanchor relocation in the first base station. The SMF or the UPF maydetermine whether to perform anchor relocation in the first base stationbased on at least one of the RAI or downlink information for pendingdownlink data. The SMF or the UPF may determine not to perform anchorrelocation in the first base station. Based on the determining, the SMFor the UPF may send an indication comprising the determining to the AMF.For example, the SMF or the UPF may send the indication via the PDUsession update procedure and/or the PDU session modification procedure.The AMF may determine not to perform anchor relocation based on theindication. Based on the determining not to perform anchor relocation,the AMF may send a N2 resume response message (or a path switch responsemessage) to the first base station wherein the N2 resume responsemessage may comprise a suspend indication requesting to suspend RRCconnection. Based on receiving the N2 resume response message, the firstbase station may send a retrieve UE context failure message comprisingan RRC release message. Based on receiving the N2 resume responsemessage and the RAI indicating that a downlink data transmission isexpected (e.g., a single downlink data transmission and no furtheruplink data transmission is expected), the first base station may waitfor the downlink data. Based on receiving the downlink data, the firstbase station may send a retrieve UE context failure message comprisingan RRC release message wherein the RRC release message may comprise thedownlink data. Based on receiving the RRC release message, the secondbase station may forward the RRC release message to the UE.

FIG. 29 illustrates an example of an enhanced procedure for mobileoriginated small data transmission with anchor relocation in RRC idlestate. A wireless device or UE may be an RRC idle state with suspendingRRC connection. An old base station (e.g., anchor base station or firstbase station or source base station) may have stored UE context. The UEmay have small uplink data. Based on the small uplink data, the UE maydetermine to perform a user plane EDT procedure. Based on thedetermining, the UE may send an RRC resume request message, uplink (UL)data and (AS) RAI to a new base station (e.g., non-anchor base stationor target base station or second base station). The second base stationmay send a retrieve UE context request message to the first base stationwherein the retrieve UE context message may comprise the UL data and theRAI. Based on receiving the UL data, the first base station may send theUL data to the UPF. For example, based on receiving the UL data, thefirst base station may send the UL data via the N3 connection of the UEto the UPF. Based on an RRC state of the UE being an RRC idle state withsuspending RRC connection, the first base station may send a N2 resumerequest message comprising the RAI to an AMF. The AMF may determine toperform anchor relocation based on at least one of the RAI or downlinkdata information for pending downlink data. Based on the determining,the AMF may send a N2 resume response message to the first base stationwherein the N2 resume response message may indicate the determining.Based on receiving the N2 resume response message, the first basestation may send a retrieve UE context response message comprising UEcontext of the UE to the second base station. Based on receiving theretrieve UE context response message, the second base station may send apath switch request message to the AMF. Based on receiving the pathswitch request message, the AMF may send a path switch response messageto the second base station. Based on receiving the path switch responsemessage, the second base station may update the path fortransmitting/receiving control signalling and user data of the UE. Basedon receiving the path switch response message, the second base stationmay send a UE context release message to the first base station. Basedon the UE context release message, the anchor may release the UEcontext. Based on the updated path, the second base station may forwarduplink user data from the UE to the UPF and forward downlink data fromthe UPF to the UE.

In an example of FIG. 29 , additional signaling may need for path switchprocedure comprising the path switch request message and the path switchresponse message. The downlink data transmission may be delayed due tothe additional signaling.

FIG. 30 illustrates an example of an enhanced procedure with signalingoptimization for mobile originated small data transmission with anchorrelocation in RRC idle state. A wireless device UE may be an RRC idlestate with suspending RRC connection. An old base station (e.g., anchorbase station or first base station or source base station) may havestored UE context. The UE may have small uplink data. Based on the smalluplink data, the UE may determine to perform a user plane EDT procedure.Based on the determining, the UE may send an RRC resume request message,uplink (UL) data and (AS) RAI to a new base station (e.g., non-anchorbase station or target base station or second base station). The secondbase station may make a path switch request message for the case that anAMF determine to perform anchor relocation in the first base station.The second base station may send a retrieve UE context request messageto the first base station wherein the retrieve UE context message maycomprise the UL data, the RAI and the path switch request message. Basedon receiving the UL data, the first base station may send the UL data tothe UPF. For example, based on receiving the UL data, the first basestation may send the UL data via the N3 connection of the UE to the UPF.Based on an RRC state of the UE being an RRC idle state with suspendingRRC connection, the first base station may send a N2 resume requestmessage comprising the RAI and the path switch request message to anAMF. The AMF may determine to perform anchor relocation based on atleast one of the RAI or downlink data information for pending downlinkdata. Based on the determining, the AMF may send a N2 resume responsemessage to the first base station wherein the N2 resume response messagemay comprise a path switch response message. Based on receiving the pathswitch response message, the second base station may update the path fortransmitting/receiving control signalling and user data of the UE. Basedon receiving the path switch response message, the second base stationmay send a UE context release message to the first base station. Basedon the UE context release message, the anchor may release the UEcontext. Based on the updated path, the second base station may forwarduplink user data from the UE to the UPF and forward downlink data fromthe UPF to the UE.

In existing technologies, when suspending RRC connection, there may betwo cases depending on RRC state of the UE. The anchor base station mayprovide the UE with different UE identities depending on RRC state bysending an RRC release message comprising the UE identity to the UE. Forexample, the anchor base station may provide the UE with a resumeidentity for RRC idle state with suspending RRC connection. Based onreceiving the resume identity, the UE may transition to RRC idle statewith suspending RRC connection. The UE may send an RRC resume requestmessage comprising the resume identity to the anchor base station. Theanchor base station may use the resume identity to identity thesuspended UE context of the UE in RRC idle sate. For example, the anchorbase station may provide the UE with an inactive-RNTI (I-RNTI) for RRCinactive state. Based on receiving the I-RNTI, the UE may transition toRRC inactive state. The UE may send an RRC resume request messagecomprising the I-RNTI to the anchor base station. The anchor basestation may use the I-RNTI to identity the suspended UE context of theUE in RRC inactive sate.

In existing technologies, the anchor base station in New Radio (NR) mayuse same UE identity for both, RRC idle state with suspending RRCconnection and RRC inactive state. The anchor base station may providethe UE with the same UE identity (e.g., I-RNTI) for both RRC state bysending an RRC release message comprising the same UE identity to theUE. Based on receiving the UE identity, the UE may not identify whichRRC state the UE may transition to.

In an example embodiment, the anchor base station may provide the UEwith RRC state information by sending the RRC release message comprisingthe RRC state information. Based on receiving the RRC state informationwherein the RRC state information may indicate either an RRC idle stateor an RRC inactive state. For example, the RRC release message maycomprise the RRC state information and the UE identity. Based onreceiving the RRC state information, the UE may transition to the RRCstate in the RRC state information.

In an example, the anchor base station may request the UE to transitionto an RRC inactive state. Based on requesting the UE to transition toRRC inactive state, the anchor base station may provide the UE with theRNA configuration (parameters) by sending the RNA configuration in theRRC release message wherein the RRC release message may further comprisea UE identity (e.g. a resume identity or I-RNTI). Based on the RNAconfiguration, the UE may transition to RRC inactive state. The anchorbase station may request the UE to transition to an RRC idle state (withsuspending RRC connection). Based on requesting the UE to transition toRRC idle state, the anchor base station may not provide the UE with RNAconfiguration (parameters) by sending the RRC release message withoutthe RNA configuration wherein the RRC release message may comprise a UEidentity (e.g. I-RNTI). Based on the RRC release message, the UE maytransition to an RRC idle state.

A first base station may send, to a wireless device, a first radioresource control (RRC) message requesting to suspend RRC connection. Thefirst base station may receive, from a second base station, a firstmessage requesting a wireless device context of the wireless device,wherein the first message comprises release assistance information (RAI)of the wireless device. The first base station may determine, based onthe RAI, to keep the wireless device context of the wireless device. Thefirst base station may send, to the second base station and based on thedetermining, a second message indicating a failure to retrieve thewireless device context, wherein the second message comprises a secondRRC message requesting to suspend or release RRC connection of thewireless device.

The first RRC message may further request the wireless device totransition to an RRC inactive state.

The determining may further based on downlink data information forpending downlink data wherein the downlink data information may compriseat least one of amount of pending downlink data, data radio beareridentity associated with the pending downlink data or applicationinformation associated with the pending downlink data.

The determining is further based on the amount of pending down databeing smaller than a data threshold.

The RAI may comprise at least one of expected data transmissioninformation, data radio bearer identity associated with datatransmission, application information associated with data transmissionor amount of expected data.

The expected data transmission information may comprise at least one ofno further uplink and no further downlink data transmission is expected,a single downlink data transmission and no further uplink datatransmission is expected or more than single uplink or downlink datatransmission is expected.

The amount of expected data may comprise at least one of amount ofuplink data or amount of downlink data.

The determining is based on the amount of expected data being smallerthan the data threshold.

The first base station may postpone, based on the RAI indicating that asingle downlink data transmission and no further uplink datatransmission being expected, to send a response message for the firstmessage until receiving the single downlink data from the UPF whereinthe response message comprises at least one of the second message or aretrieve UE context response message.

The first base station may send, based on receiving the downlink dataand/or the determining, the second RRC message comprising the downlinkdata.

The first base station may be different from the second base station.

The first base station may store, based on sending the second message,the UE identity and a cell identity of the second base station.

The first RRC message may comprise at least one of a resume UE identityof the wireless device, a next hop chaining count, radio access network(RAN) notification area information or period RAN-based notificationarea update timer value.

The first message further may comprise at least one of the resume UEidentity of the wireless device, a cell identity of the second basestation or uplink data of the wireless device.

The second RRC message may comprise downlink data of the wirelessdevice.

The second RRC message may be an RRC release message.

The first message may be a retrieve UE context request message.

The second message may be a retrieve UE context failure message.

The first message may comprise the data threshold.

The second base station may determine the data threshold based on atleast one of signaling quality between the UE and the second basestation, UE capability, expected arrival time of expecteduplink/downlink data or expected resource for expected data transmission

The data threshold may comprise at least one of a data threshold foruplink data transmission or a data threshold for downlink datatransmission.

A first base station may send, to a wireless device, a first radioresource control (RRC) message requesting to suspend RRC connection. Thefirst base station may receive, from a second base station, a firstmessage requesting a wireless device context of the wireless device,wherein the first message comprises release assistance information (RAI)of the wireless device. The first base station may send, to an accessand mobility management function (AMF) and based on an RRC state of thewireless device being an RRC idle state, a first N2 message requestingto resume N2 connection wherein the first N2 message comprises the RAI.The first base station may receive, from the AMF, a second N2 messagerequesting to suspend RRC connection. The first base station may send,to the second base station and based on the second N2 message, a secondmessage indicating a failure to retrieve the wireless device context,wherein the second message comprises a second RRC message requesting tosuspend or release RRC connection of the wireless device.

The AMF may determine, based on the RAI, to keep the wireless devicecontext of the wireless device.

The determining may be further based on amount of pending downlink databeing smaller than a data threshold.

The AMF may send, to the first base station, the second N2 message basedon the determining.

The first RRC message may further request the wireless device to enterin an RRC idle state.

The first RRC message may comprise at least one of a resume UE identityof the wireless device or a next hop chaining count.

The first N2 message may comprise at least one of a UE context resumerequest message or a path switch request message.

The second N2 message com at least one of a UE context resume responsemessage or a path switch response message.

A second base station may receive, from a wireless device, releaseassistance information (RAI) of a wireless device and a radio resourcecontrol (RRC) resume request message requesting to resume RRCconnection. The second base station may send, to a first base station, afirst message requesting a wireless device context of the wirelessdevice, wherein the first message comprises the RAI of the wirelessdevice. The second base station may receive, from the first basestation, a second message indicating a failure to retrieve the wirelessdevice context, wherein the second message comprises a second RRCmessage requesting to suspend or release RRC connection of the wirelessdevice. The second base station may send, to the wireless device, thesecond RRC message.

The second base station may be different from the first base station.

Sending the first message may be based on UE context of the wirelessdevice not being in the second base station.

The second base station may receive, from the wireless device, theuplink data wherein the uplink data is multiplexed with the RRC resumerequest message.

The second base station may receive the RAI via a medium access controlcontrol element (MAC CE) wherein the MAC CE comprises the RAI.

A wireless device may receive, from a first base station, a first radioresource control (RRC) message requesting to suspend RRC connection. Thewireless device may select a cell of a second base station based on asignal quality of the cell exceeding a data threshold. The wirelessdevice may send, to the second base station, an RRC resume requestmessage requesting to resume RRC connection and release assistanceinformation (RAI) of a wireless device. The wireless device may receive,from the first base station via a second base station, a second RRCmessage.

The wireless device may suspend, based on the first RRC message, RRCconnection.

The first RRC message may further indicate an RRC state of the wirelessdevice wherein the RRC state comprises at least one of an RRC inactivestate or an RRC idle state.

The wireless device may transition, based on the first RRC message, theRRC state.

The wireless device may send the RAI via a medium access control controlelement (MAC CE).

1. A method comprising: sending, from a second base station to a firstbase station, a request for a context of a wireless device, wherein therequest comprises assistance information for a small data transmission(SDT) procedure of the wireless device, the assistance informationindicating whether: single data associated with the SDT procedure isexpected; or more than single data associated with the SDT procedure isexpected.
 2. The method of claim 1, wherein the first base stationsends, to a wireless device, a first radio resource control (RRC)message indicating a suspension of a RRC connection of the wirelessdevice.
 3. The method of claim 2, wherein the first RRC messagecomprises at least one of: a resume wireless device identity of thewireless device; a next hop chaining count; radio access network, RAN,notification area information; and period RAN-based notification areaupdate timer value.
 4. The method of claim 1, wherein the first basestation determines, based on the assistance information, whether to keepthe context of the wireless device.
 5. The method of claim 4, furthercomprising: determining to keep the context of the wireless device basedon no further uplink or downlink data transmission being expected; anddetermining to not keep the context of the wireless device based on morethan a single uplink or single downlink data transmission beingexpected.
 6. The method of claim 1, further comprising receiving, by thesecond base station from the first base station and based on determiningto keep the context of the wireless device, a second RRC messageindicating a release or a suspension of the RRC connection.
 7. Themethod of claim 1, further comprising receiving, by the second basestation from the first base station and based on determining to not keepthe context of the wireless device, the context of the wireless device.8. The method of claim 1, wherein the assistance information comprises adata radio bearer identity associated with the SDT procedure.
 9. Themethod of claim 8, further comprising: determining to keep the contextof the wireless device based on a data radio bearer associated with thedata radio bearer identity being configured for small data transmission;and determining to not keep the context of the wireless device based onthe data radio bearer associated with the data radio bearer identitybeing not configured for small data transmission.
 10. The method ofclaim 1, wherein the assistance information comprises applicationinformation associated with the SDT procedure.
 11. A second base stationcomprising: one or more processors; and memory storing instructionsthat, when executed by the one or more processors, cause the second basestation to perform operations comprising: sending, to a first basestation, a request for a context of a wireless device, wherein therequest comprises assistance information for a small data transmission(SDT) procedure of the wireless device, the assistance informationindicating whether: single data associated with the SDT procedure isexpected; or more than single data associated with the SDT procedure isexpected.
 12. The second base station of claim 11, wherein theoperations further comprise sending, to a wireless device, a first radioresource control (RRC) message indicating a suspension of a RRCconnection of the wireless device.
 13. The second base station of claim12, wherein the first RRC message comprises at least one of: a resumewireless device identity of the wireless device; a next hop chainingcount; radio access network, RAN, notification area information; andperiod RAN-based notification area update timer value.
 14. The secondbase station of claim 11, wherein the operations further comprisedetermining, based on the assistance information, whether to keep thecontext of the wireless device.
 15. The second base station of claim 14,wherein the operations further comprise: determining to keep the contextof the wireless device based on no further uplink or downlink datatransmission being expected; and determining to not keep the context ofthe wireless device based on more than a single uplink or singledownlink data transmission being expected.
 16. The second base stationof claim 11, wherein the operations further comprise sending, to thesecond base station, based on determining to keep the context of thewireless device, a second RRC message indicating a release or asuspension of the RRC connection.
 17. The second base station of claim11, wherein the operations further comprise sending, to the second basestation, based on determining to not keep the context of the wirelessdevice, the context of the wireless device.
 18. The second base stationof claim 11, wherein the assistance information comprises a data radiobearer identity associated with the SDT procedure.
 19. The second basestation of claim 18, wherein the operations further comprise:determining to keep the context of the wireless device based on a dataradio bearer associated with the data radio bearer identity beingconfigured for small data transmission; and determining to not keep thecontext of the wireless device based on the data radio bearer associatedwith the data radio bearer identity being not configured for small datatransmission.
 20. A system comprising: a second base station comprising:one or more processors and memory storing instructions that, whenexecuted by the one or more processors, cause the second base station toperform operations comprising: sending, to a first base station, arequest for a context of a wireless device, wherein the requestcomprises assistance information for a small data transmission (SDT)procedure of the wireless device, the assistance information indicatingwhether: single data associated with the SDT procedure is expected; ormore than single data associated with the SDT procedure is expected; andthe first base station, wherein the first base station comprises: one ormore processors and memory storing instructions that, when executed bythe one or more processors, cause the first base station to performoperations comprising: receiving the request for the context of thewireless device.